firstly わたしはけいかんです is a valid sentence, google translate is just notoriously bad at translating Japanese. One of the reason why it didn't come out as you thought it would is probably because you are using just hiragana. Google translate has a hard time figuring out where the words start/end in that case. 私は警官です is a lot simpler to parse and should probably give you the answer you expected.
secondly it's おこっています because of grammar. you are seeing the construction て-form + いる. the て-form is a verb conjugation roughly translating to "and" (it's a bit more subtle than that, but we're going to ignore that for now) and its used to string actions together. There are some verbs you can come across after the て-form which then take on a more grammatical meaning as opposed to a literal one. such as みる (try to do), ください (please do), いる (be doing), etc. So おこっています is being angry, おこってです is ungrammatical because you are not stringing actions together and です is not one of those special verbs.