Glue from a hot glue gun doesn't work too good at holding plastic together.
I've tried gluing plastic together using glue guns and glue gun hot glue sticks and it held the plastic together for a short while.
But then eventually the plastic came apart after a few days so the hot glue didn't really hold the plastic together too long.
You can melt plastic together though and use a plastic spoon or plastic knife to bond the plastic together which will work much better than hot glue will on plastic.
Hot glue works best on porous surfaces such as fabric or even paper but doesn't work too good on non porous surfaces such as plastic, metal etc.
You can buy some glue that will usually bond plastic together but melting the plastic together to weld the plastic works much better.