Tips for singing?

Hey,

There is a musical group at my school that I take part in.

I got a bigger role in the next musical (omg).

I'm going to play the narrator from the musical "Joseph and the Amazing Technicolor Dreamcoat," but I'm worried that I won't be able to do it perfectly vocally, as the narrator sings quite high (at least in the songs on Spotify and in the film adaptation on YouTube).

How can I improve my head voice or make it stronger?
And how can I "expand" my chest voice? Because at a certain pitch, I feel like I have to force my chest voice out of me, haha. It definitely doesn't feel easy.

Are there any tips or good YouTube videos with good exercises?

LG