Requesting some natural translations

こんいちは I would like some help for some "natural" translations. By this i mean not a literal translation but more the way you actually say it. The reason for it to sound actual natural because its a stream with real japanese ppl and while i don't understand 99% of what is getting told i still enjoy it and would like to at least communicate on the very lowest lvl by just saying "hello" "goodbye" "welcome back" and such. "I have to go" in the sense i am about to leave the stream. "bye,cya" when actually going away (i know there is さようなら and じゃね but neither seem to fit when you still need to stay polite and its only for a while so sayounara seems inappropriate) I might add some more depending on the need for them. Some help would be very appricated. ありがとうございます

Hmm.... For "I have to go", you could say "Ikanakute wa ikanai".....but that's more literal....maybe "Ikanakucha" or "Ikanereba naranai"....I'm not entirely sure... For "bye, cya", you could say "Soredewa mata" or "Dewa, mata ne". "Dewa" is a more formal version of "Ja.." well, I hope that helps :)