Some of the machines broke down quite often, but when things like these happened we just called a technician. - correct the sentence

You should aim to arrive at any time that's convenient for yourself. - correct the sentence

I'd always wanted a smartphone and when I was given it as a birthday present, I thought it was wonderful. - correct the sentence

The lecturers will give you a detailed explanation of the subject. You may not be able to understand all, but you should be able to get a general idea. - correct the sentence

There are several umbrellas in the stand in the hall. I'd advise you to take it if you're going for a walk. - correct the sentence

There was a long queue at the ice cream parlour because most of the children wanted it. - correct the sentence

I wasn't happy about my hotel room. I said it to the receptionist but she didn't do anything about it. - correct the sentence

We're looking for a new accountant and it is why I am writing to you. - correct the sentence