If you want to hold a note longer, there are several symbols to use. You can use a fermata, you can dot the note, you can just play a longer note, etc. If you want to play a note slightly louder, you accent it. The accent looks something like this, >. If you want to hold a note for it's original length, leave the note as is.
Explanation:
These are all answers from a tired piano player, if you're looking for help with a strings instrument then you should probably ignore me.
