"I have a friend's tea."
Translation:저는 친구의 차가 있습니다.
They don't really have lessons, but if you pay attention to the structures of the sentences they do give you to translate, you'll start to notice a pattern. When I first started learning Korean I thought the sentence structure was going to be one of the things I'd have the most trouble with because it's so different from English, but it's really just observation and intuition, at least for me.
I hope this help
자는= i + topic marker (는). Another topic marker is 은 the only difference is tha wea use it when the word ends with a consonant, eg: 빵은
친구의= friend + (의) a possession marking particle. Is like the ['s] in English.
자가= Tea + (가) subjet marker, another subjet marker is 이 we will use it when a word ends with a consonant (eg. 빵기) and we use the 가 when the word ends with a vowel.
있습니다= It means there is/ to existed/ to be located. It is a verb that indicate existence. (It can also mean 'to have')