How hard is 800 ELO as a complete newbie?

I've never played something like AOE before, I mostly play offline games and my online PvP experience extends to Valorant and Rocket League. My GF is very into AOE and I would like to get more into it and hopefully play with her in the recent future.

She shared a lot of tutorials by Hera and Spirit of the Law to get started with and I played some of the early tutorial campaigns on my own. Thing is I can't play the game right now since I don't have access to my PC so I want to learn as much theory as I can before I start playing online. I watched some of the T90 tournaments to get more idea but their plays are so optimized I can't exactly follow without the fundamentals. What resources should I go through?

Suppose I can start physically playing the game a month from now and can learn the correct theory fundamentals till then, how long would it take for me to reach 800 ELO? I think there is a Max Elo difference required for ranked 2v2 and I would like to get as close as possible before I start ruining her games.

Any help is appreciated.