Verb conjugation of "unbutton" in English

The billing of additional working hours is not justified, since it was our request to download the software and wait for the new version. They have admitted the error of the translation.
I remember once again how I failed as a student, mainly in French class. Since I have lived in Russia, it was not easy to learn other foreign languages. The alphabet is also different.
I do not like London, my home is in southern England, and there is a lot of work there too. A lot of people are moving to London just for work. I've been here for 10 years and I am studying chemistry.