I've got tonsallitus several times is that normsl? Any advise to prevent it?

Tonsillectomy. Recurrent tonsillitis is neither "normal" nor "abnormal"... It's just you. There's really not much you can do to prevent it other than general hygeine to prevent upper respiratory infections (cold) - wash your hands, minimize touching your face. If you want maximal prevention... Then have your tonsils removed.