Korean sentences are formed with.. Subject + Object + Verb. But subject can be easily omitted and so does the object. Verbs are usually not deleted and used in a conversation. However, I think you are asking for a bigger picture, like a whole basic Korean grammar. If you want to know deeper, I guess you have to study deeper with the Korean grammars.. The ones you are askings are the basic ones, so a lot of sites are willing to help you to learn it besides Italki. There is a good site called 'How to study Korean'. : http://www.howtostudykorean.com/ The documents there might as well help you with understanding the basic Korean grammar. Plus, there is a site called : Talk to me in Korean : http://www.talktomeinkorean.com/ They are more focusing on listening and speaking, but it will be a help also. So hope you can have fun time learning. : )

If you want to go beyond simple sentences, the next thing you might look at is conjunctions (but, and) and other sentence/clause connectors (because, so) and things like (instead of, without). Then you can join sentences and clauses and make your sentences more interesting.

Please give us some example sentences which you feel difficult.