They are used in different ways. "This is such a great idea". "This is so amazing." "So" and "such" are not interchangable in these examples. But, you can say: "This idea is so great." (although a bit unnatural) "This is such an amazing thing." Just look for more examples to get the hang of it.

"We'll talk it later" is incorrect.

Studying must be done wisely. You have to study multiple things, in multiple ways, abd find the right balance for yourseld. In this case, it will always be "the more you study, the more you know, the wiser you get." It doesn't matter if you forget somethibgs sometimes. You can forget specific things but you can't forget their experiences and what they made you become and advance as a human... Plus you can always remember whatever it is you forget.

Also, you should put a comma after "everyone".