「着替えが終わり次第レッスンします。」

= Kigae ga owari shidai ressun shimasu.

= I will start the lesson as soon as I finish changing my outfit.

「僕のように日本語がうまくなるかどうかはみんなの努力次第です。」

= Boku no you ni nihongo ga umaku naru ka douka wa minna no doryoku shidai desu.

= Whether your Japanese gets as good as mine or not depends on your efforts.