A user commented that: Gerunds are often used when action are real, fixed or completed and Infinitives are often used when actions are unreal, abstract or future. But I don't know how to apply it here. Being operated on may be a traumatic experience. OK To be operated on may be a traumatic experience. OK Why didn't you just send me out prowling around nightclubs? OK Why didn't you just send me out to prowl around nightclubs? OK That glut of cars in the market is not good for the business, IT is making us lowER the prices. That glut of cars in the market is not good for the business, IT is making us lowER the prices. NEITHER WORKED FOR THESE SENTENCES. The market is to team up with that product, focusing on its useless. The market is teaming up with that product, to focus on its useless. It’s a rip off buying a magazine, they are teemed with publicity. This doesn't work. It’s a rip off to buy a magazine, they are teemed with publicity. OK, but I wouldn't use 'teemed' a more natural way is 'filled'. First, congratulations! You are doing a great job!! You put in a great effort and I admire your determination. You did very well, I did find some mistakes, however not many on the usage of the verbs you were concentrating on. a person is 'operated on' when you are paired together on a project you are 'teamed up' round and around are not the same word, you can however shorten around by writing 'round the apostrophe allows you to drop the a, but that is normally only used in dialog or musical lyrics the car sentence did not make sense using either form, you could rewrite that as " this is causing us to lower the prices" OR "we started lowing the prices"

It is useful to get the simple things right before going on to hard stuff. There are too many silly mistakes in all of your sentences, and they have nothing to do with the gerund or the infinitive. Half the sentences don't even make sense. Sorry, but it is hard to correct sentences that don't mean anything.