In heaven, we will be able to remember the friends who were on Earth and in the seven gates of heaven? Say if a person was in the first gate, will he be able to go to the second, third, fourth, etc.
Yes we will not only remember our friend but we will also meet them.
Allah tells us that the people of Paradise will approach each other and question each other about their lives on the Earth, discussing how they used to be and the difficulties that they used to face. This will be their topic of discussion while they take drinks and meet together, socializing and reclining on couches, while servants attend to them, bringing them all goodness in the form of food, drink and apparel, the likes of which no one has ever before seen, heard, or even imagined.” [Tafsîr Ibn Khathîr]
here is Quran verses:
Allah says: “And those who believe and whose families follow them in faith, We shall reunite them with their families; nor shall we deprive them (of the fruit) of aught of their works: Each individual is in pledge for his deeds.” [Sûrah al-Tûr: 21]
In this verse Allah says that He will bless the believing family members that he shall bring them together in Paradise. This will take place by raising the status in Paradise of the children who fell short of their parents’ status to the levels in Paradise attained by their parents. This is by Allah’s immense generosity and favor.
Ibn Kathîr relates the following that Ibn `Abbâs said regarding the above verse:
These are the children of the believers who die on belief. Then, if their fathers attained a higher level in Paradise than they did, they will follow their fathers, and none shall have any of their good deeds reduced. [Tafsîr Ibn Kathîr]
Abû Nu`aym relates on the authority of Hamîd b. Hilâl that:
“I has been conveyed to us that the denizens of Paradise, the higher and lower grades from among them, shall visit each other.”
There are several hadîth about the the people of Paradise visiting one another; however, all of those hadîth are weak. They are mentioned by Abû Nu`aym in Sifât al-Jannah (258-260) and by Ibn al-Qayyim in Hâdî al-Arwâh ilâ Bilâd al-Afrâh (332-336).
And in heaven is one human can meet each other even if they enter from another gate example. On the judgement day all seven gates will call him to go through them them.