Is there any website/resource for dungeons/raids mechanics?

I am new player and sometimes I struggle with mechanics in dungeons .sny website/resource that explains how to counter boss mechanics or such ?

There are tons. Ff14 wiki does good, hector guide, mtq, u have discords for that. Mainly go on youtube type in what dungeon you need guide for

When I need a refresher for mechanics, I just look up "ffxiv [duty name]" on Google, and one of the first three results is usually the FFXIV Consolegameswiki.

https://ffxiv.consolegameswiki.com/wiki/FF14_Wiki

They do a pretty good job at explaining the mechanics, though it's usually all text and no images, so hopefully you're good at visualizing.