Does breaking Salah without any reason make you a kaafir? Do you cease to be a muslim ?
Bismillah. All praises and glory is to Allah.
Your question is a little bit unclear, but i will try to answer as good as possible.
As long as one belive that there is one god (Allah) and that prophet Muhammad (pbuh) is his final messenger, then you are a believer.
Every person have different level of iman (faith). That level of iman will make you feel worse when you sin. A person with high iman will immediately out of fear and love for Allah repent. He will also strive to be best in deeds.
Salah is the most important thing that were given to human kind. Therefore we have to read salah. If we dont pray which is a sin or do other sins, it will be bad for us in the hereafter. However Allah is all forgiving, most merciful and will forgive as long as you keep repenting to him.
While you are reading salah you are in a conversation with Allah. There is a very special connection. You cannot break your salah for no reason and just walk away. If you do this because you dont belive then you are a kaafir but if you break salah while you belive, then it will be a great sin and you should repent and do it correctly.
If you have to break your salah because of any emergencies, then break it correctly and read it later.
Allah says in Surah al-mulk: ˹He is the One˺ Who created death and life in order to test which of you is best in deeds. And He is the Almighty, All-Forgiving.
So this world is about doing good deeds. If you want to succeed then you should read salah properly.
Also never forget that Allah is the most merciful, and all forgiving. He will forgive you even if your sins are as large as the sea. The best part is that Allah loves you, so dont be sad.
I advice you to read Quran and watch series on youtube related to islam. I also advice you to repent and read your salah properly.
Hope that answers the question.