Translation of momentum in Spanish

You can always write me and we can learn together any language you want. How long you have taken classes? Was it only at night or on weekends? Makes me wonder how someone can be so fluent in Spanish.
I will be creating an additional study with a student (his name is Juan), which may appear in local newspapers in the future (in English). However, this may take a couple of weeks too.
Thanks again for your letter. For now, the weather here is like it is in your country, ice cold. I will write you a letter in Spanish and in English. So you can compare the sentences.