interruptions in wifi internet connection

Hi, I often have sudden interruptions in my wifi internet connection in my macbook; they last up to five minutes. Even though it seems that I am properly connected to my network, I am actually not online.

This doesn’t seem to be related to my internet provider, because in the same time the connection in my ipad and iphone is properly working.

Usually I run network diagnostics in the macbook and the problem is quickly repaired. But with does it appear in the first place?

Any ideas ?

Many thanks for your suggestions.

Kind regards,

E