Player Jumps instead of moving forward

Hey, I am a rookie developer. I know a little bit of C# and C++. I also know a bit of JavaScript. But I have this problem that pisses me off. I made my player, I placed it close to the ground (not touching it to make sure it doesn't get stuck) and when I try to move forward, my player doesn't move. Instead, it goes jumping around like crazy. I've checked the script and changed the grounded to True. But it doesn't work. Obviously that's not the problem. But I don't understand why this happens if it's the already-made first person asset of Unity!