I'll be <there> in five minutes ---> 5 ふん で いきます

Anytime!

Thank you so much Ryoko. (Sorry, autocorrect). ありがとうございます。

Thank you so Mich Ryoko.

I see, in this case there are several ways of saying depending on the person. (私は)5分で始(はじ)めます。I'll start in 5 minutes. (私は)5分で行きます。I'll go in 5 minutes. (私は)5分で合流(ごうりゅう)します。I'll join in 5 minutes. However, I think you can use the casual form with your friends, so I would say: 5分後に始めるよ / 行くよ！ After some conversations, like "see you in 5 minutes!" (じゃあ、)5分後に！ I hope this was helpful.