Wow, I am impressed. You can now skateboard and ollie. This means that you can now move forward and jump. The next step is easy, all you have to do is learn how to turn on flat ground and on ramps. Its super simple and you will be able to do this just as fast as you were able to start riding a board.
There are multiple ways to turn. The first way is to just lean. This is the easiest way but you are not able to do sharp turns, but it is the beginning of the process to being able to turn. With leaning, just turn the bottom of your foot from being parallel to the ground to it being angled in the direction that you would like to turn. In order to not fall off of the board you need to lean your center of mass toward your turn. See, its easy dont worry. Start off slow and as you practice you can speed up and do sharper turns.
Next, you get to learn how to kickturn. This might sound complicated, but it really is not. All that you have to do is shift some of your weight from your front foot to your back foot like you would in the start of an ollie. One difference though is that you need the tail of your board not to touch the ground so that you do not fall or get razortail. Then you turn your body in the direction that you would like to go and reshift you wieght back to how you feel comfortable when skating. This means that your front wheels will leave the ground, but hopefully when you find your balance after your turn your wheels will be on the ground. Now you are able to turn! If you have any issues I have included a video so that you are able to see how you can fix your turning.
Now that you can kickturn on flatground, you can learn how to do it on a ramp. For some, this might be even easier. At least in my case it is because as you go up the ramp you slow down so as long as you time it right you will be turning while you have no velocity. In order to kickturn on a ramp all that you have to do is do exactly what you were doing on flatground. The only difference is that you have to commit fully and do a full 180 or 360 degrees. I'm so proud of you. You can now kickturn on a ramp. See how easy it was.
Lastly, I am going to teach you how to manual. A manual is just a wheelie where you are balancing on your back two wheels. If you can kickturn this should be super simple. Just do the same weight shift like you did for the kickturn and dont turn or slide your front foot like an ollie. Just hold your balance and then when you are about to loose it just shift your weight back to both feet and you will land normally. Its that basic. I believe in you!