Learn Polish: Wracam z pracy. - I am coming back from work.

In Polish, the verb ending usually tells you who is doing the action. The -m at the end of wracam already means "I return" or "I am returning". You only need to add the word for "I" (ja) if you really want to emphasize it.

Does wracam mean "I come back" or "I am coming back"?

It means both! Polish doesn't have a separate continuous tense like English does. Depending on the situation, wracam can translate to "I return", "I am returning", "I come back", or "I am coming back".

I thought z meant "with". Why does it mean "from" here?

The word z changes its meaning depending on the situation. When you use it to talk about accompanying someone or something, it means "with". But when you talk about moving away from a place, like coming back, it means "from" or "out of".

Why is the word for work pracy instead of its basic form praca?

Prepositions in Polish force the words that follow them to change their endings. The preposition z meaning "from" requires the following noun to use the Genitive case. To do this, the feminine word praca drops its -a and takes an -y ending, becoming pracy.