Writing is probably one of the most difficult language skills for second language learners.
It is here that the ESL learner must apply the grammar they are studying. Just because you can do well on grammar tests doesn’t mean you can write well. It is here where vocabulary, grammar and writing come together. If you can write good sentences and can organize your thoughts, you should be able to write well.
Practice applying the grammar you are learning. Take a grammar point and several different words and try to write several sentences. Have someone check your sentences. Next, try to combine the sentences using conjunctions. Or put the sentences together in a paragraph. It’s not that hard.
Here are some helpful writing websites:
Finally, this website explains about the differences between simple, compound and complex sentences and includes some practice.
And for writing essays,