Integrity matters
There are many words in German and English that sound similar but have very different meanings. They are called “false friends”.
(PERSON) OF INTEGRITY
CRITICISM
CRITIC
Leistung can also have a financial meaning. In this case, we translate it as benefit or payment: Ich bekam in den USA keine Leistungen im Krankheitsfall. “I received no sickness benefits in the US.”
When Leistung describes the energy or yield produced by something (for instance an engine or a factory), we talk about capacity,output, performance or power: Diese Maßnahmen könnten die Leistung schnell verdoppeln. “These measures could quickly double the output.”
By the way, if you have completed a Leistungskurs, you can call it an advanced course: Ich besuchte den Englisch-leitungskurs.
“I took the advanced course in English.”