Pet friendly flat for one person

I'm a 32-years old person who is going to work in Berlin and is looking for a Flat. I don't mind it to be big/small as long as it is cozy, well illuminated, with balcony (I really wish that, but not mandatory). I don't mind whether it has or not furniture.

I work as a data engineer, I hold a degree in mathematics and a Master's degree in Logic. I speak Spanish, English, and during the way, I've learned some Italian, Portugues and even Catalan. I enjoy a lot learning languages.

Since I'm Colombian, I might have some people a year to stay at my place, but it usually would mean for either couple of days or tourist purpose. So, I never expect my guests to be a lot hanging out at my place, but out in the streets instead.

I enjoy activities that either require to be outside (as hiking or swimming) or board/online games.