If you want to do well in grammar, you have to know different things well. For example: Tense, Parts of speech, right forms of verb, suffix-prefix, transformation of sentences. These have to be practiced well. You can practice grammar by installing the Hello English app from the Play Store. Pay close attention to grammar classes in school classes. You can learn grammar from my academy: digital book blog. You will learn grammar from various channels on YouTube like Robi Ten minute school, English moja, technical English learning home etc. Practice free hand writing. Watch English subtitles in different movies. Practice different topics of grammar. If you follow these, you will be able to improve your grammar.