It is incorrect to use 'cause' in that sentence. I am learning English because it is necessary for my career. 'Cause is a possible shortened version of because. The apostrophe is absolutely essential if you want to write it that way. "Cause" without the apostrophe means something very different from "because" and cannot be used in the same way. It is also pronounced However shortening 'because' to 'cause is a feature of informal spoken English. Importantly, there is absolutely NO reason to do it in normal writing. It is not a standard contraction like 'I ' is for 'I am', for example.

Cause it's the short way to say because. Cause it's very informal, and you can usually find it in songs, whatsapps ... Other examples of shorted words are : gonna (going to) , wanna (want to) ...