My s20+ screen doesnt turn on but from the vibrations it seems on.

From the symptoms you're describing it seems most likely that the screen has died - as you surmised, probably from the moisture. Unfortunately, the only fix is going to be to replace the screen.

Your phone, like many Android phones, has two different methods to replace the screen. The safest and recommended way is to purchase a screen that's already mounted to the midframe, then transfer the internal parts from the old phone to the new one. On something like an iPhone this would be a daunting task, but Samsung actually makes the job straight-forward. Here's a guide from the Spanish site Nadie Me Llama Gallina that shows how to do that replacement.

Manuales / Samsung Galaxy S20+ / Fullscreen - Nadie Me Llama Gallina

The other way to do it is to separate the old screen from the midframe and glue on a new display. The procedure for this is entirely different from the screen+midframe procedure; in some ways it's simpler with less parts to remove, but that's balanced against the need to glue the screen back on the midframe. That's the method shown in the iFixit guide to screen replacement.

Samsung Galaxy S20 Plus Screen Replacement - iFixit Repair Guide

Generally the screen alone is a couple of dollars cheaper than the screen+midframe assembly, but that tends to be offset by the need to purchase glue. One advantage to the first method is the screen is already mounted on the midframe and should theoretically be more secure and more water resistant than what you can do at home.

So it will be your decision as to which method you want to use; I prefer the screen+midframe method myself, as it's not particularly difficult and saves you from having to mess with glue, which has the potential to get into the OLED and damage it.

One note I will pass along from experience is that you need to be careful with removing the rear cover. The glass is very thin and easier to break than you might think; I was doing a screen replacement for a friend on a Samsung and yes, I did break the rear panel. I replaced it at my own expense since it was entirely my fault, so don't be me - use lots of heat, maybe some isopropyl alcohol (90% or higher concentration) and lots of patience.

Good luck with your repair. Be sure to come on back and let us know how it all turns out and anything you learned from the experience.