Learn Polish: Wszechstronny ekspert zna nie tylko tę dziedzinę, ale i wszystko inne. - The versatile expert knows not only this field, but also everything else.

They all mean "but also" and are interchangeable in the structure nie tylko ..., ale .... However, ale i is slightly punchier and feels very idiomatic in everyday Polish when linking two parallel concepts like tę dziedzinę and wszystko inne. You can safely use ale także or ale też if you prefer.

Why is it tę dziedzinę and not tą dziedzinę?

In standard written Polish, the accusative (direct object) singular form of the feminine pronoun ta (this) is tę. While you will often hear native speakers say tą dziedzinę in casual speech to rhyme with the noun's -ą ending, tę dziedzinę is the strictly correct form you should use in writing.

How is the adjective wszechstronny (versatile) constructed?

It literally means "all-sided." It combines the prefix wszech- (all or universal, as seen in wszechświat, meaning the universe) with the adjective stronny (related to sides, from the noun strona). This perfectly describes an expert whose knowledge covers multiple sides or angles.

Why does the word for "else" take the form inne here?