How to raise the floor level in a frame house?

I have a half-timbered house. On the 1st floor, the bathroom is equipped with screed and underfloor heating. And now the bathroom floor is 55 mm higher than the main floor. In addition, tiles are laid in the bathroom. So in the end the difference will be about 70 mm. The rest of the flooring will be vinyl.

What can I do about it? Leave it as it is and just put a threshold? Or is there a way to compensate for this? But with what? Even three layers of plywood are only 54 mm thick.