Is it normal to wear a belt with suspenders?
Depends.It depends
You can wear a belt with suspenders, but most people see it as redundant since they do the same job. If you like the look or find it comfortable, it’s your call.
It’s not the usual choice: a belt and suspenders both hold your pants up, so wearing both can look a little like you’re preparing for a pants-related emergency. In some settings, people consider the combination a fashion faux pas.
That said, it’s harmless, and style rules are optional. If you like how it looks or have a practical reason, go for it—just know some people may find it unusual.