So I got my new tongue piercing three days ago and I've been trying to eat soft stuff, wash my mouth with listerine, warm sea salt. But there's this white stuff coming out from the bottom. Is this normal ?

I hope you are mixing sea salt with warm water and gargling. I would discontinue the listerine, that doesn't happen to be a good choice.

I don't know what you mean by white stuff?

I used a mouth wash called Corsodyl after I had my tongue pierced, also did the usual gargling with salt water. If it gets worse or swells, go see your doctor. You may be advised to take it out. I have had mine for 10 years and I haven't had any problems since the first week or so after having it done, so hopefully yours will be the same.

The artist people said the sea salt with water and the listerine would be okay .

Listerine is okay for freshening breath, but not if you have an open wound in your mouth, as you do have with the piercing.

Listerine was strongly disregarded by my piercer. If you use mouthwash, only use nonalcoholic ones. Listerine is too strong. I've never had any issues with "white stuff." So my guess is that, it may be from the listerine.

Well good news.. my tongue healed ! (:
But another question..
How long do I have to wait until I can drink coffee again.

I would wait a week just in case to drink coffee... that is, if it's not swollen or doing anything else funky.

Listerine is fine as long as it's the kind with zero alcohol and be sure to mix it. Use half mouthwash and half water.