Helen, they do not all mean capacity. die Leistung = performance die Fãhigkeit = ability, capacity Therefore, "die Leistungsfãhigkeit" is "the capacity to perform" and "competitiveness".

First of all, these are all nouns, so they are all capitalized. "Leistung" is the actual performance delivered by a person or an engine. "Fähigkeit" is any kind of ability. Thus, "Leistungsfähigkeit" is the ability to perform, which is usually determined by technical details of a machine or the level of training and the health condition of a person (plus some external factors).