To take the OP a little seriously. The sort of amphib ops the Allies were running were really tough to stop. The Germans tried multiple techniques & it came down to seldom enough combat power at the critical point. Anzio was the closest they came & Kesselring accomplished that through a combination of a huge reserve & thorough plans set in place long before the battle. Even with that it took Churchills overconfidence, Alexanders lack of attention, & the transfer of too many amphibs to the UK. The original concept outlined in October 1943 suposed a larger & rapid follow up. The ability to land seven or eight divisions, three corps & a army HQ in a couple weeks as with Op Husky would have created a situation Kesselring could not have coped with. He'd probably have made a imeadiate decision to retreat to Rome or further, vs waiting three months until April.
Kesselring was disadvantaged in Sicilly by the Allied deception operations. The German leaders were at a loss to predict where the Allies might attack next & scattered both their front line forces and reserves across the entire south European littoral. Concentrating up to three armored corps & the entire Axis air forces to defend Sicilly might have done it, but as pointed out here earlier the Allies could have then attacked elsewhere. Perhaps at two place since the Axis defense would be weaker elsewhere.