Best Tuning for Audi S5, 3.0l V6, Mild Hibrid

Hello you knowledgeable people, I always lived with the impression that an Audi S5 is faster than a Golf GTI, until last night when I learnt otherwise🤦‍♂️ embarrassing that was. Either I’m a bad driver or that car had been tuned up. I prefer the 2nd choice. Any S5 owners here that done any modifications to their cars, like Stage 1 or 2 or whatever to make their cars maybe quicker and more responsive? I know about cars but I know nothing about tuning, I’ve read some topics around but looks like opinions differ from one place to other. Would be nice if someone can recommend any garages, having taken the car and what the results were? As well as what the pros and cons are in doing such a thing. I live in East Anglia region so even better if there’s any place around me, don’t mind travelling but only if necessary to get the best result. Thank you in advance for taking your time and sharing some thoughts