Hi! Welcome to PokeBase! I saw your post about New Sw/Sh Team. If you want to learn about competitive Pokemon, this Youtube Playlist is a series called "Pokemon Academy" created by 2016 Pokemon VGC (Video Game Championships) world champion Wolfe Glick that is basically an introduction to competitive Pokemon. Wolfey is one of the best players EVER, so I highly recommend his YouTube channel.
https://www.youtube.com/playlist?list=PLb_5fF_O3FviC-jM32a72uQXfqWXTr-8i
It's worth noting that VGC is a double battles format, so if you want to do singles, check out PokeAimMD, who is considered Wolfey's singles equivalent, and has a great, informative YouTube channel as well. I've linked a video to a teambuilding guide of his, but whether you pick Singles or Doubles, watching the Pokemon Academy lecture "EVs, IVs, and understanding the damage calc" is really helpful to understanding competitive pokemon, probably the most important out of any of these links.
https://www.youtube.com/watch?v=rA_ZdOjIc3c
I hope this is useful. Have fun with competitive Pokemon!
