If you are a creative worker like a designer or writer, [then] you must avoid overworking.

The 'then' in this sentence is optional. Although 'best practice' would be to include it, it is almost never included in speech or informal writting.

How to be a "cCreative" cCreative wWorker?.

Titles have important words as capital letters. You are giving instructions not asking as question so you do not need the question mark.

If you are a creative worker, like a designer or writer, you must avoid overworking.

You need an indefinite article in front of designer. You can put one in front of writer as well but the one in front of designer carries over so you can do without.

Capitalize on your spare time to play and to learn with whatever resonates with you, and, after that, you will become more creative and productive.

You don't need the "with". You can simply "learn something".