No, that's wrong. Improved is called verbessert, or more often besser.
verbesserte is valid only as an adjective, e.g. Der verbesserte Fehler (The corrected misspelling), or as a verb in certain grammatical cases, e.g. Er verbesserte den Fehler (He corrected the misspelling).
Improved strength would be "erhöhte Festigkeit", and improved car would be "besseres / verbessertes Auto".
The domain is worthless.