Hi Philip,
Here you have to accept that the two languages do not always function in exactly the same way. In this case in English we use "relaxing", a gerund forum, as an adjective. In Spanish there is an adjective form that stems from the verb "relajar", to relax, which is relajante. It is a separate word from the gerund form of relajar, relajando. Ignore the -te here, it is just a part of the word itself and carries no 'tú' meaning.
Hope this is clear and good luck with your learning!
Also, just in general be careful with Google translate! It is not at all perfect. Although since you're asking humans here on italki you're on the right track :)