I don't know where to get started speedrunning Doraemon, it might be worth making a Discord for Doraemon not just as a community dedicated to a game in particular, but a community for speedrunning the series as a whole, just my 2 cents (for reference, dark souls 1, 2 3 + elden ring + demon souls all lead to the same discord server, they just use different channels)
I regularly organize events for this game and have its discord channel. This is where I describe the strategy and other information about this game. I do not know if discord channels for other Doraemon titles exist. If you want to start a speedrun of this game, you can help by inviting me to the discord channel.
@SynthGirl64 I highly recommend Shimono san's server, They help explain many games and the japanese community is very helpful and excited to have new runners.
The other discord I would join in addition is anime speedruns discord https://discord.gg/k5wmNCSaVE since Doraemon games get a bigger platform there, and we have a lot of fans and contributors to all anime games, as well as its a great place to promote, discuss topics. Even if your not a runner of the game you can still participate with the awesome community there or contribute in someway to an anime game or anime game series of your choice.
Good luck on yours runs, thank you for the good question.