I have committed major sin of adultry, am i still forgivable if i ask forgiveness

ASALAMUALAKUM my name is rehan and i am 15 years old for the past 7 months i have been online schooling but i have been engaged in porn first but then i started being engaged in masturbation i have been doing it for months and i cannot talk to anyone else about it because i am too shameful to talk about it but few days ago i learned that it is a major sin and i am very scared cause i am afraid there are punishments for it as well please tell me are there any? But i want to ask forgiveness from Allah now please tell me if i stop doing it and promise not to do it again and ask forgiveness can i still be forgiven from Allah?