'Ability' and 'faculty' could be both synonyms referring to skills, talents, powers and capacities of the body or the mind ,whether acquired or naturally inherent. However when you use 'faculty', you rather refer to the inherent capacity than the acquired one. One's 'ability' could be acquired through learning and training or inherently and naturally given. You could say: "His ability to speak English improved through intensive practice." Since it is obviouslly an acquired skill in this context, you can't interchange it with 'faculty'. "He has a special faculty in solving intricate mathematical equations." Here it is apparently a natural and inherent talent. You could still use 'ability' instead of 'faculty' in this sentence, but then the emphasize would be on the skill and talent and it won't be clear ,whether it is inherent and naturally given or an acquired skill.

thank you anyway

I suggest www.thefreedictionary.com

I suggest www.thefreedictionary.com

A dictionary would tell you.