I’ve personally used LMMS. It’s an open-source program available for Linux, Windows and Mac. It is used to produce sounds, has a big variety of instruments, and ability to make something really custom.
i’m struggling with sounds effects and music
Unfortunately, as most other programs out there, this one has a learning curve. Some knowledge of Music Theory will help to quickly make something that sounds nice, although it’s not a requirement. There are plenty of tutorials online to help with that.