I have a Russian bolt action sks and a guy told me it could be converted into semi. Is this true? And if so how?
There is no such thing as a bolt action SKS. Possibly it is a Mosin Nagant? Post a couple of pictures and we'll be able to help you with it.
A semi-auto Mosin would be interesting, I have to admit.
That is possible, but unlikely. I would call that a broken SKS, not a bolt-action SKS. That is why a picture would be helpful.
The Yugoslav sks does have a gas cut off that was used for grenade launching. It would in effect make it a bolt action if you were firing normal bullets.