I'm a native speaker. Normally, it works like that (90%), but just as in any languages, you'd find exceptions. For example, mar, farol are masculine. Colher is feminine.
I'd suggest you to look it up in a dictionary. They normally state if the word is male or female.
https://www.priberam.pt/DLPO/colher "substantivo feminino"
If you can't, follow your guts!