how do i focus on studying without friends?

Im currently a highschool student, recently my grades have been really bad cause i focus on my friends and also focusing to not be a "loner" if that makes sense?

i dont wanna be known as a loner, yes my studies are important but i want friends too🥹, i spent years of my life not having friends at all and i was called weird cause all i did was study

i also found out one of my closest friends was talking behind my back and telling her other friend everything i was saying and im minimizing my contact with her, its super awkward actually, i randomly distanced myself from her because of it and she noticed

i just need tips on how to study and learn better, how to stop hyper fixating on friends that aren't probably gonna stay with me till college, and how to not be a loner too?

Please give me tips and advice that you have that you would tell your younger self, harsh or not I'll accept advice since i have no one else to talk to at all, thank you so much🥹