Buying first bike, need advice?
 

Hi, everyone. My name is Sasha, I'm 18 years old. I'm buying my first bike this year and there are three bikes that I really like, 1985 ninja 600r, 1983 unitrack GPZ 550 and a 1983 GPZ 750, would these bikes be too powerful for a beginner? I don't have a lot of riding experience I have ridden my friends 200cc dual sport a couple of times.

As a beginner, I'd be more worried about buying an over-30 year old bike. You'll likely be fixing many problems.
It's generally easier, and safer, to learn on a smaller, lower powered bike. With a smaller one, you can learn to wring out all the power it has and have fun doing it. With a powerful bike, wringing out the power can get scary and dangerous quickly.

Only you know how much self-control you'll have. I didn't have much when I was a young beginner. For me, smaller and less powerful was the smarter choice.

Regardless which bike you decide to buy I suggest taking a motorcycle driving class. You will learn so much about riding safely it'l be well worth the money.