Exercises with comparatives

http://www.englisch-hilfen.de/en/exercises/adjectives_adverbs/adjectives_comparison_sentences.htm
http://www.englisch-hilfen.de/en/exercises/adjectives_adverbs/adjectives_comparison_sentences2.htm
http://www.englisch-hilfen.de/en/exercises/adjectives_adverbs/adjectives_comparison_as_as.htm

Exercises on American English

http://www.englisch-hilfen.de/en/exercises/british_american/index.php
http://www.englisch-hilfen.de/en/exercises/languages/be_ae.htm
http://www.englisch-hilfen.de/en/exercises/languages/be_ae2.htm
http://www.englisch-hilfen.de/en/exercises/languages/be_ae3.htm

Exercise on prepositions: time, place and direction

Exercise on prepositions: time, place and direction
http://www.englisch-hilfen.de/en/exercises/structures/prepositions_place_time.htm

Exercises on verbal tenses

1. Exercises on Simple present and present continuous
http://www.englisch-hilfen.de/en/exercises/tenses/simple_present_progressive.htm
http://www.englisch-hilfen.de/en/exercises/tenses/simple_present_progressive2.htm
http://www.englisch-hilfen.de/en/exercises/tenses/simple_present_progressive3.htm
2. Exercises on Simple past and past continuous
http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_progressive.htm
http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_progressive2.htm
3. Exercises on Simple past and present perfect
http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_present_perfect.htm
4. Exercises on will-going to
http://www.englisch-hilfen.de/en/exercises/tenses/will_going_to_future.htm
5. Exercises on simple past and past perfect
http://www.englisch-hilfen.de/en/exercises/tenses/past_perfect_simple_past.htm

Grammar Exercises - Articles

You can try to do exercises 1,2 and 3
http://www.englisch-hilfen.de/en/exercises_list/artikel.htm