Seeking Guidance on Duas for Repentance and Concealment of Sins

As-salamu alaykum, I've been searching for duas to seek repentance for my major sins, but I'm feeling a bit lost on which ones to focus on. I know sincerity is key, but some guidance would be really helpful. I'm also looking for duas to make when I don't want my sins to be exposed in this life or the next. I'm in a difficult situation where someone close to me has found out about something, alhamdu lillah they're discreet, but I still want to make dua to keep it private. I've been trying to do istigfar daily, but I have to admit, I'm scared that my sins might be too big to be forgiven. I know Allah forgives with sincerity, but it's only human to feel a little scared, right? Sorry if I'm getting a bit overwhelmed. Jazakum Allahu khairan for any advice or duas you can share.