how do i improve my communication with people

i'm not good at communication and interacting in general and online, if someone messages me i leave it too long to reply, because i'm not good or confident in writing back, also i'm scared of rejection or writing something that comes over as ' too eager' then frightening the other person off? there's some good people on here who have reached out to me in the pms, but because i left it too long to reply...they gave up and moved on, then i feel regret, because i could of made a good friend.

and a good friend is what i need right now.