Learning grammar must be done by understanding the structure or formulas in tenses in English. As has already been explained in the previous post, there are 16 English tenses that the formula must be mastered. Apart from that, you may go to http://britishlifeskills.com to take the English exam to get the UK visa.
The structure is the basic foundation in learning Grammar. All tenses in English need to be understood. If you can understand, it will be easier to apply Grammar in English. One example is the present continuous tense which means that the event is happening. This Present Continous has the formula:
S + to be + verb + ing form
Example: I am drinking a glass of juice.
It is important to remember that the formulas can guide you in composing sentence after sentence that is in accordance with grammar and perfect. By understanding the English structure, of course, you will be able to master English-language grammar which will have an impact on the mastery of perfect grammar.