Hi all. We will be in Berlin in April and am looking for an apartment for 2 people - a 1 bdrm with a sleeper sofa or a 2 bdrm. Any suggestions? Instead of asking for neighborhood recommendations - are there any areas we should avoid?

Also, I'm trying to figure out the trains - is there one website you prefer for checking out train options? Will we need a res to take the train from Dresden to Berlin?

Thanks for your insights!

For schedules visit: https://www.bahn.com/en/view/index.shtml

For loads of info on train travel and how to buy (cheap) tickets see: https://www.seat61.com/

Can't help with the apartment, I stayed in a hotel.

Thanks - I have that train app already on my phone - it was a great one to figure out how to get around Holland when I was there.

I also forgot to ask - are there any particular apartment rental sites for Berlin that are good ones?

It's kinda hard to say which areas to avoid in general aside from suggesting to stay in a more central district.
Any place with a 10xxx zip code would be okay for starters. Or within the downtown freeway loop (if you got a map, that's the A100 freeway).
Since you will need to use public transport anyway, any specific location should be in easy walking distance to a subway or suburban train station (U-Bahn or S-Bahn).

The overwhelming majority of apartment rentals in Berlin is on airbnb.
Berlin has imposed some restrictions on short-term subletting without approval by the districts' governments, so the whole airbnb business is a bit of a grey area. But those restrictions are currently challenged in court, so it's not the same situation as in some other cities where short term rentals have become illegal or where a registration number in the ad shows you that the rental is legally okay.