How long is it gonna take me to become a decent DM?

hello everyone, i know this question might sound funny (it sounds funny to me) but im willing to start DMing and i dont know where to start, my friends told to just read the book and it feels like its gonna be long. me and my friend group wanted to run a campaign for a while and they asked me to work on something since im the only one that plays DnD in the group but i dont know how to be a DM, got any tips or maybe some good place to start?