Verb conjugation of "trade" in English

After next week, I will tutor the Mr. Zillmay from the language lab in Los Angeles, he is currently in the states. The lesson will take place in LA, but it may be held no earlier than mid-February.
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 am in my German lesson and I'm learning about the subjunctive. I had never heard about it before. Can you ever deal with all Verb conjugations? I just totally misunderstand the past tense!