Hallertau Mittelfrüh is an aroma hop but it is often used for bittering (or all the way through the boil) in lightly hopped German lagers. If you want to use slightly less total hops, bittering with Magnum first and layering on some Hallertau Mittelfruh is very classic.
Note for 2023/2024 Noble hops from Europe have been affected by several environmental factors pushing the alpha acids (bittering strength) down much lower than typical. It's hovering around 2-3% right now so buy enough to acheive your IBU goals.
Hallertau Mittelfrüh - or "Hall Mitt" - hops have a specific aroma descriptors include mild, yet spicy, with floral and citrus tones. Although it can be and is used throughout the boil, it is most prized for its fine, elegant aroma and flavor contribution. Mittelfrüh is, at least to some, the epitome of noble hops.