Why can't I do a forward tumble?

I think that when you say forwards tumble you mean forwards roll.

It sounds like you are performing it incorrectly by putting the top of your head down on the floor which is dangerous to your neck.

To learn a forwards roll crouch down and put your hands on the floor in front of you. Tuck your head in so that your chin is on your chest. This is important and yo must keep your head tucked throughout the roll until you stand up. You want to put the back of your head or neck down in the roll, not the top of your head. To begin the roll straighten your legs to push your bum up and over your hands, putting the back of your head and neck down on the floor. You will overbalance and roll forwards. Stay in a tight tuck.

You can use your hands to help you stand up at first. As you get more confident and can initiate the roll faster so that you have more momentum it should enable you to stand up without using your hands. In fact as you improve and roll faster it will be your shoulders and upper back that touch the floor first and your head won't touch at all. To do this you have to make a little jump into the roll though so when you are first starting and actually placing your head on the floor before you push off it has to be the back of your head.

A drill you may find useful is to sit in a tight tuck and roll backwards and forwards (sometimes called egg rolls.) This is a way of practising keeping the tight tucked shape while rolling. You can also try to roll back and then roll forwards and stand straight up without using your hands. It may help to try to put a straight jump on the end.

I'm the opposite. I love forward tumbling, but I hate going backwards (because I can't see where I'm going idk).

Try just doing forward tumbling skills, not connected on the floor and trampoline. Then practice doing like rebounds out of the front tumbling skills (alone) or if there is a pit available, practice tumbling into the pit. I love doing that because it helps since you don't necessarily have to land it. As long as you're in the pit range you're pretty much safe! And then you can add 8 inch mats once you're feeling more confident and finally move onto the floor!!

Honestly, I have fear issues with gymnastics a lot. Ask someone to spot (although it is harder to spot front than back skills), and literally just go for it. That is the only way to overcome fear quickly. Or also you could work up to doing it but that takes forever. Hope this helped!

Try this drills first

Front limber: You’ll kick into a handstand, then lower your feet to the floor and form a bridge. From the bridge, you’ll stand back up. The front limber mimics the motions of a front handspring.

Heel drive against the wall: With a mat propped up on the wall, you’ll perform a handstand, driving your heels as quickly as possible into the mat.

Handstand pop: To perfect your shoulder block, you’ll do a handstand and immediately hop your hands off of the floor, keeping your arms straight. If this drill becomes too easy, try multiple hops before your feet come down.

Front handspring off of a springboard: You’ll follow the techniques outlined in this guide, but your hands will push off of a springboard. This drill gives you the feeling of blocking through your shoulders.

but all ways remember all it is running headstand,backbend, and stand up. You know all those skills already trust me you will do just fine. You also need to tell you tumbling coach this also, because they will be able to help.