Possibilities

Assuming that you have eight semesters total and you have completed three of them with a 2.8 average. Mathematically, the highest GPA you can get is a 3.55, assuming that you get straight A's from now on.

It depends on your situation- to get the 2.8 GPA were you not understanding the work or just not doing it? If its the ladder, then try doing some more of your work- at least the easy ones and ones which weigh the most. Also make connections with your teachers, my brother would never do homework but is super smart and was close to one of his teachers so she made an excepts that as long as he gets above a 95 on tests, he doesn't have to do the homework. This might not always happen but making a connection with teachers can be beneficial in many ways. In my brothers case, he got a 94 in the class rather than a 70 so having a connection could definently help. If your just not understanding the work, see if your teachers offer office hours or something of the equivalent where you can go and ask your teachers questions. Another great source could be the internet! I can not count the amount of things that were clarified to me by Youtube videos! This may be a longshot but you can also ask your teachers for extra credit work! They won't always say yes but you won't know unless you try! I hope this is helpful and good luck!