How to make a boost jump mechanic?

I haven't been on roblox for three years, I can't even read my own scripts code without even saying what is a variable and other lua code terms. I need some help please, add me on roblox and discord if you can help me. I have tried coding but I don't know what to type even if I look at a another script for reference. I resorting to this website since I sincerely want to script again. I wanted to make a simple boost jumping script but I don't want to use free models because how will I learn if use free models, I can't even make a simple boost jumping script for the life of me. If any of you guys can help me, thank you for replying and reading this.