Of course I am going to invite you - fine. These lessons are the best if you want to get fit - is OK. 'are the best' is probably an exaggeration, but the phrase is OK as pros you can earn money. - no. If you have given one example, it should be singular. e.g. one pro is that you can earn money. As cons you have long jours working - ditto, but also 'long working hours'. Typically 'pros and cons' is usually used as a 'placeholder phrase', to save or avoid listing, or as Eld said - to introduce a list. Even if you use them separately, it would be more common to use them in the plural, and give more than one example. But having said that - to use it in your way is not incorrect. take measures against pollution - fine.

Of course I am going to invite you - yes These lessons are the best if you want to get fit - "These lessons are good if you want to get fit" (but this sentence isn't very beautiful) as pros you can earn money . As cons you have long jours working. - hm, i don't use pros and cons like this. i'd say "there are pros and cons to the job: you can make a lot of money, but you have to work long hours" take measures against pollution - yes