Some grammar

When I read your descriptions and letters I noticed some grammar areas that you need to practice. Here are the exercises for that:

a/an

 http://www.english-zone.com/grammar/a-an.html

http://a4esl.org/q/h/9801/cg-a_an.html

was/were
www.roadtogrammar.com exercise 345

has/have
www.roadtogrammar.com exercise 120,121,122

who/which/whose

http://www.ego4u.com/en/cram-up/grammar/relative-clauses/exercises?02


http://www.englisch-hilfen.de/en/exercises/pronouns/relative_pronouns.htm