Verb conjugation of "dürfen" in German

I try to learn English as much as possible so that I can travel next year to the United States. I would agree to your proposal but I also need to find good teachers. My goal is quality and speed.
Sometimes I visit Vocabulix to meet new people. It is true that one could do the same on Facebook, but the FB page is rather for friends, and you are less likely to contact strangers for this purpose.
Many thanks for your suggestions. They are very useful. I can't answer your mail now, but I will come back to you later when I'll have more time. I hope that you and your family are well!