A few adulting questions!

Best way to build credit?!

I have a few medical bills & a broken phone under my name.

Medical bills because my mom switched our insurances, I had no idea still went to the doctors a few times & now I owe a few thousand... what can I do about that?

Also my phones a big one because I cracked the screen & went to get it fixed & the guy completely broke my phone. I was suppose to bring him to court but in between lost both of my grandparents. How long do I have to bring someone to court for an incident? It’s been like 5 months!