HERE'S A PIECE OF ADVICE!

Here's a piece of advice to all my students and to those who want to improve their learning skills. "Motivation is essential."
My suggestion would be to have a clear objective  in order to get an excellent result. 
I recommend you to start with some easy exercises, just to review what you already know. You can learn and  make improvements along the way while practising. You shouldn't take very long, just do as many exercises as you can in a short period of time.  And then, check your answers.
Failing can be your greatest teacher! 
Keep working and learning through mistakes.
Enjoy what you do!!!
Consider your abilities and try to do your best!
You will get better results if you feel motivated!
Well, you can start with the following exercises.

ACTIVITY 1.- First, go to “ENGLISH FOR EVERYONE” on the right bar. 

                          Then, click on “ENGLISH GRAMMAR EXPLANATIONS”.

      http://www.englisch-hilfen.de/en/grammar_list/alle.htm  -  On the left , click on “VERBS” .  And then, click on Grammar Exercises - Verbs

And finally, do the following exercises,

Irregular verbs 1  

Irregular verbs 2  

Irregular verbs 3  

Irregular verbs 4  

Irregular verbs 5  

Irregular verbs 6  

ACTIVITY 2.- Fill in the gaps in the exercises below.

Exercise Mix 1  

Exercise Mix 2  

Exercise Mix 3  

Exercise Mix 4  

Table - Fill-in Exercise  

ACTIVITY  3.- Now, you can do the following tests,

            Irregular verbs - randomly selected

Test 1  

Test 2  

Test 3  

Test 4  

Test 5  

 GOOD LUCK and ENJOY YOURSELF WITH ENGLISH!!!