In Berlin you get nowhere near the 120-130k as a senior dev, at least not on average. There may be some (very rare) exceptions.
Living in a 80-90sqm flat without carpet or broken stuff, in an area where you have bars and cafes and restaurants and a decent school, plus sending a child to nursery, doesn’t seem unattainable in Germany (at least my German friends say so). In London that’s luxury.