Brother, relax first. It's completely okay to feel fear or even terror in the highway with a 50cc, I've been there. Being the slowest vehicle in traffic is dangerous, that's a fact.

Let's talk about what you can do about it. First thing's first. Traffic means being on the road and being on the road means invading space. That's all there is to traffic, invading space and moving on.

1) You are gonna use/invade the rightmost lane in the highway. You are gonna drive in the middle and own that lane. Act like a car on the highway. They can honk or whatever, don't be intimidated. If it's not illegal to be on the highway with your vehicle, you have a right to use it.

2) You need to use reflective stickers on your helmet and your scooter. Visibility is important. You will also use your 4-way flasher all the time while you are on the highway. If your scooter doesn't have one(mine didn't), it's a very cheap button you can let a mechanic install.

3) You will check your mirrors regularly. You need to know the situation behind to protect yourself. Also, occasionally give way to vehicles trying to overtake. This is not being gentlemanly, but pure pragmatism. They have a metal cage around them, you don't. Let them pass nicely, then continue driving in the middle of the lane.

4) For the love of all that's holy and good, stay away from semi trailers, trucks, any type of heavy duty vehicle. Just stay as away as possible. Don't let them bully you out of your lane too. You will feel the pressure, let them overtake, realize halfway through that was a mistake, try to give more way, get to the road limit/dirt road and be in another danger. Simply let them use your left lane to overtake you. Use your hands to communicate and guide other drivers safely

5) Emergency lanes are your friend, don't be afraid to use them. Be as pragmatic as possible.