I there a way to double the count of everything without changing the time signature?

I was doing a score for a song, while transcribing and notating I realized there are semiquavers in the melody. I want the score to be more simpler, so I would like to double the time, so the semiquavers become quavers. And two chord a bar becomes one chord a bar.

Wanna ask if there's a way to do this without changing the time signature? I have inserted the chords and a bit of melody. Retyping the whole thing will take much time.

Thx in advance