Only Have 1st And 2nd Gear

Could be that your tranny is going or just something simple. I would check the tranny fluid level first. Usually that is done after you take the vehicle for a short drive. Park it on a level surface and check the level while in park with the car running. If it's low, that could be the problem. Add fluid and see if that solves the problem.

If the fluid level is okay, check the condition of the fluid. Is it red and clear or is it brown and dirty looking? If it's brown, do a transmission fluid and filter change. That may straighten it out.

The third possibility is a vacuum leak. Some transmissions use vacuum to shift, especially shifting into third. Probably not the problem, but it can't hurt to check for leaks if the first two suggestions don't work.

It could also be that your shifter linkage needs adjustment. I've had cars that refused to shift into third because the linkage was out of adjustment.   You would need to buy a repair manual for your specific vehicle to be able to adjust it correctly.