Identify whether your filters are baffles or cassettes before soaking, because Franke uses both and cassettes have an internal structure that needs longer in the water. Work the stainless or glass canopy along its grain with nothing abrasive.
Franke is a Swiss kitchen systems brand, and unlike almost every other name in this series the rangehood is a lead product rather than the third item in a package. That inverts the usual hierarchy: on a Franke kitchen the hood is frequently the most considered appliance in the room.
Baffle or cassette
Franke uses both, and they are not cleaned identically.
Baffles are overlapping angled plates with channels between them. Soak flat and brush along the channels rather than across.
Cassettes are a sealed metal box containing layers of mesh or a labyrinth structure, and the important difference is that you cannot see or reach the interior. A cassette that looks clean from outside can be well loaded inside, and it needs a considerably longer soak than a baffle to let hot water and degreaser penetrate to the middle.
If a Franke cassette is not coming up after an hour, give it two with a change of water rather than concluding it is finished. The general method is on our rangehood cleaning guide.
Designer canopies show everything
Franke hoods go into designer kitchens, and they are frequently glass and stainless rather than plain steel, hung where they are meant to be looked at.
Work stainless along the brushed grain and never across it. Glass canopies take a soft cloth and warm soapy water, then a dry buff, and nothing abrasive at any point on either material.
The rest of the kitchen
Franke ovens and hobs exist and are the secondary products. See how to clean a Franke oven and how to clean a Franke cooktop.
What actually goes wrong
A cassette declared finished after a single soak that never reached its interior.
Swirl marks on a designer canopy.
An impeller nobody has reached, which is where the noise comes from.
Should you do it yourself?
Do it yourself for the filters, allowing longer than you would for baffles if yours are cassettes.
Get someone in for the impeller housing, particularly on a canopy that is a feature of the room.