I suggest some websites to practice Grammar
http://www.englishpage.com/verbpage/verbs1.htm
http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/simcon1.htm
http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/simcon2.htm
http://www.better-english.com/grammar/presforms.htm
http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-12052.php
http://www.englisch-hilfen.de/en/exercises/tenses/simple_present_progressive2.htm
http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-13846.php
http://www.ego4u.com/en/cram-up/grammar/simpre-prepro/exercises
http://perso.wanadoo.es/autoenglish/gr.prescon.i.htm
http://www.englishlearner.com/tests/present_simple_continuous_quiz_1.shtml