This … out of ten scale isn't popular among German speakers. It's one of the markers to spot an U.S. american (or people who watched too many U.S. sitcoms.)
Most German speakers use … % or fractions instead.
Ich bin zu 90 Prozent von ihrer Idee überzeugt.
I am 90 percent convinced of your idea.
Ich habe dich nur zur Hälfte verstanden.
I understood only half of what you said.
Drei Viertel der Zeit haben wir angestanden.
Three quarters of the time we stood in queues.
For communicating skills (aside from grades) you should not use a scale at all but tell what your latest/best skill is, as that is far more informative. German speakers don't do so much small talk but expect information. It's not uncommon to admit insignificant/understandable weaknesses and it will make you sound totally German.
Ich verstehe Deutsch schon sehr gut, wenn mein Geprächspartner langsam und deutlich spricht.
Deutsch sprechen kann ich noch nicht so gut.