First of all, you have to understand that as long as Allah allows you to live, for so long the doors of Repentance and Forgiveness are open.
The Prophet (ﷺ) said: "Indeed, Allah accepts the repentance of a slave as long as (his soul does not reach his throat)." At-Tirmidhi (3537) and Abu I'sa graded it Hasan Gharib
"Say: O I'badi (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allaah, verily, Allaah forgives all sins. Truly, He is Oft‑Forgiving, Most Merciful" [Al-Zumar 39:53]
And also do not ever forget:
The Messenger of Allah (ﷺ) said: “Allah Almighty said: O son of Adam, if you call upon Me and place your hope in Me, I will forgive you despite what is within you and I will not hesitate. O son of Adam, if you have sins piling up to the clouds and then ask for My forgiveness, I will forgive you without hesitation. O son of Adam, if you come to Me with enough sins to fill the earth and then you meet Me without associating anything with Me, I will come to you with enough forgiveness to fill the earth.” At-Tirmidhi (3540) and it is classed as Sahih by Sheikh Albani
Allah's Messenger (ﷺ) said: “Allah is more pleased with the repentance of His slave than anyone of you is pleased with finding his camel which he had lost in the desert.” Al-Bukhari (6309)
Allah's Messenger (ﷺ) said: "If somebody commits a sin and then says: 'O my Lord! I have sinned, please forgive me!' and his Lord says, 'My slave has known that he has a Lord who forgives sins and punishes for it, I therefore have forgiven my slave (his sins).' Then he remains without committing any sin for a while and then again commits another sin and says: 'O my Lord, I have committed another sin, please forgive me,' and Allah says: 'My slave has known that he has a Lord who forgives sins and punishes for it, I therefore have forgiven my slave (his sin). Then he remains without Committing any another sin for a while and then commits another sin (for the third time) and says: 'O my Lord, I have committed another sin, please forgive me,' and Allah says: 'My slave has known that he has a Lord Who forgives sins and punishes for it I therefore have forgiven My slave (his sin), he can do whatever he likes." Al-Bukhari (7507)
"By Him in Whose Hand is my life, if you were not to commit sin, Allah would sweep you out of existence and He would replace (you by) those people who would commit sin and seek forgiveness from Allah, and He would have pardoned them." Muslim (2749)
Because you mentioned that you had cried about your sins:
The Prophet (ﷺ) said: "There are seven whom Allah will shade on a day when there is no shade but His. […], and one who remembered Allah in private and he wept." Al-Bukhari (660)
The Messenger of Allah (ﷺ) said: "A man who wept out of the fear of Allah shall not enter the Fire until the milk returns to the udder; and dust in the cause of Allah and the smoke of Hell shall not come together." At-Tirmidhi (1633) graded Sahih
The Prophet (ﷺ) said: "There are two eyes that shall not be touched by the Fire: An eye that wept from the fear of Allah, and an eye that spent the night standing on guard in the cause of Allah." At-Tirmidhi (1639) graded it Hasan Gharib; but Abu I'sa also said: 'There are narrations on this topic from U'thman and Abu Rayhanah.'
The Prophet (ﷺ) said: “The Hellfire is forbidden for the eye weeping from the fear of Allah. The Hellfire is forbidden for the eye vigilant in the way of Allah. […]“ Sunan al-Kubra (8818) and Sheikh Albani graded narrations of this type Hasan li Ghayrihi
The Prophet (ﷺ) said: "There is nothing more beloved to Allah than two drops and two traces: A teardrop shed out of fear of Allah […]" At-Tirmidhi (1669) graded Hasan
And it is noteworthy to mention this:
The Messenger of Allah (ﷺ) said: "The one who repents from sin is like one who did not sin." Ibn Majah (4250), At-Tabarani in al-Mu‘jam al-Kabir (10281), Abu Nu‘aym in Hilyat al-Awliy'a (4/210), al-Bayhaqi in Al-Kubra (20561) | Its men are thiqat (trustworthy), except that Abu ‘Ubaydah did not hear from his father, so it is munqat'i (interrupted). See: At-Tahdhib (5/65); but it is proven because of corroborating evidence, therefore some of the scholars classed it as Hasan and others classed it as Sahih: Ibn Hajar said in al-Fath (13/471): 'Its isnad is Hasan'; Ibn Muflih said in al-Adab ash-Shar'iyyah (1/87): 'Its men are all 'thiqat' (trustworthy); Hasan according to Al-Albani in Sahih al-Jam'i (3008)
Therefore, Shaykhul-Islam Ibn Taymiyyah said:
"The one who repents from sin is like one who did not sin, and if the sin is removed, then the punishment and consequences are also removed." From Sharh al-U'mdah (4/39)
"The one who repents from sin is like the one who did not sin; as that is the case, he is included among those who fear Allah and thus deserves that Allah should grant him relief and a way out, for our Prophet Muhammad (blessings and peace of Allah be upon him) is the Prophet of mercy, so everyone who repents will have a way out according to his teachings, unlike the teachings of those who came before us, for among them the one who repented would still be punished with penalties such as killing themselves and so on." Majm'u al-Fatawa (33/35)
If you have lost track of all the sins you have done, you can then say this general Du'a:
The Messenger of Allah (ﷺ) used to say while prostrating himself: "O Lord, forgive me all my sins, small and great, first and last, open and secret. (اللَّهُمَّ اغْفِرْ لِي ذَنْبِي كُلَّهُ دِقَّهُ وَجِلَّهُ وَأَوَّلَهُ وَآخِرَهُ وَعَلاَنِيَتَهُ وَسِرَّهُ)" Muslim (483)
There are many supplications that are narrated about seeking refuge from the torment of Al-Qabr, especially reciting Surah al-Mulk before going to bed that will protect you from it inshallah.
If you truely feel remorse for your sins, then you repent and seek forgiveness from Allah and intend to never get back to your former life, Allah will not only forgive you, but also: Allah says in [Al-Furqan 70:71]: "As for those who repent, believe, and do good deeds, they are the ones whose evil deeds Allah will change into good deeds. For Allah is All-Forgiving, Most Merciful. And whoever repents and does good has truly turned to Allah properly."
Allah's Messenger (ﷺ) said: "I know the last of the inhabitants of Paradise to enter it and the last of the inhabitants of Hell to come out of it. He is a man who would be brought on the Day of Resurrection and it will be said: 'Present his minor sins to him, and withhold from him his serious sins.' Then the minor sins would be placed before him, and it would be said: 'On such and such a day you did so and so and on such and such a day you did so and so.' He would say: 'Yes.' It will not be possible for him to deny, while he would be afraid lest serious sins should be presented before him. It would be said to him: 'In place of every evil deed you will have a good deed.' He will say: 'My Lord! I have done things I do not see here.' I indeed saw the Messenger of Allah laugh till his front teeth were exposed." Muslim (190a)
And if you want to improve yourself, then understand the above and read the following:
“Have Taqwa of Allah wherever you are, and follow an evil deed with a good one to wipe it out, and treat the people with good behavior.” At-Tirmidhi (1987) graded Hasan
Continue to pray 5 times a day, to pray the Sunnah parts of those 5 prayers, to say the Adkhar after each obligatory prayer, the specific ones in the morning and afternoon, on maghrib and before you go to bed at night, to educate yourself in Islam everyday (as much as you can, without being extreme and overbearing yourself) to know what is bid'ah (innovation) and what is the authentic Sunnah, to avoid sins as best as possible; and if you sin, then remember to do this:
The Messanger of Allah (ﷺ) said: "When a servant (of Allah) commits a sin, and he performs ablution well, and then stands and prays two rak'ahs, and asks pardon of Allah, Allah pardons him." He then recited this Ayah [Al-I'mran 3:135]: "And those who, when they commit indecency or wrong their souls, remember Allah" - End Quote of the Hadith - [...] and seek forgiveness for their sins - and who can forgive sins except Allah? And [who] do not persist in what they have done while they know." Narrated in Abu Dawud (1521) and Sheikh Albani classed it as Sahih
The Messanger of Allah (ﷺ): "Whoever prays four before Adh-Dhuhr and four after, Allah makes him prohibited for the Fire." At-Tirmidhi (427) graded Sahih
