#1
So I’ve been progressing at a decent pace but I’ve hit a wall that is due to my strumming technique. I can do barre chords, power chords, basic chords, some scales but my strumming is causing me to pull my hair out. The problem I’m having is that on the upstroke when I switch chords I’m either doing it too fast or too slow. I’ll either have the chord ring out then die right away when I switch to a new chord or I’ll switch too late and mess up when I’m down stroking. I’ve tried the technique of counting 1 & 2 & 3 &, I’ll attempt to change chords on the “&” but I still am not timing it right or something. I’ve also tried up stroking a little faster to get the chord to ring allowing me a little extra time to change but I realized that I can’t constantly remember to do that. Does anyone have any tips/ideas how I can fix this?
#2
I can only recommend practice - lots of it.

But when I learned to play chords (or started learning would probably be a better way to put it) I had about 20 Beatles songs that I played. Try to get 4-5 different easy songs (Take for instace Ache With Me by Against Me! very simply to play) and just keep playing them. It is not something that will happen in a week or two, but over time you will be better.

And with barre chords, just strum all the chords from E to E up the neck one by one and try to make them all sound. Eventually you will get there.
#3
Like the last guy said, I would recommend trying to get down a couple of really easy songs to start with and practice them a lot. When I started out, I couldn't change between chords at all, but my guitar teacher gave me a progression to play that switched from E to Am to Dm and back again. The progression is really useful because the E and Am chords have very similar shapes, but then you switch to the Dm, which is different, but still pretty similar.