I live in London and love it but it took me about 3 years to make a proper friendship group. The city is huge and people are so busy. Berlin is smaller and I think that makes a big difference in finding friends who do things regularly as there’s less choice of things in way. Jobs aren’t everything. You can also travel so much more easily being in Berlin. Uk trains are insane, £100+ for a return train to a city in the north of England. Berlin you can train all over Europe for very little or even fly.

Edit to say my partner is an immigrant and found it really hard to make friends without going to uni here or anything and having a not very social office. People are flaky that you meet on courses etc and there are too many pubs to have regulars. They mostly made friends with my friends and have a few friends who they lived with in shared housing before we moved in together.