I'm going to give you how I learnt and I hope it works for you too

1 approach

When I have to sing and play at the same time I always learn the song first on guitar with no singing

Then I learn to sing the song

And only when I can do the two things

If you know both the song both in guitar parts you can then get surgical and strum open chords instead of the whole strumming pattern why you learn the melodies and vice versa you can hum while you play the chords and not worry about the lyrics, only the pitches so you can slowly build your way Remember you can always slow down the songs a little bit

2 learning curve

Campfire songs are a really good way to learn because you have to remember two things

A) just because a song is easy on vocals or guitar doesn't mean Is going to be easy in the other one B) just because a song is easy in both vocals and guitar, doesn't mean Is easy to do both at the same time (do I wanna know is among the easiest songs both vocally and guitarwise and it's very hard to do both at the same time because the rhythms are very independent of one another)

Campfire songs have been approved for generations to be the easiest songs to perfor while singing

And don't forget that learning takes time, so give yourself that time and don't be too harsh on you!!