Work / Soon in Warsaw from Budapest. Job opportunities for a musically-trained person and proofreader in Poland. [9]

There are translation agencies and corporate/law firms in Warsaw that hire native speakers as proofreaders, but you may have to do a bit of searching to get into one of those. Most if not all of the many language schools would require a recognised TEFL certificate. Good luck.

Work / Soon in Warsaw from Budapest. Job opportunities for a musically-trained person and proofreader in Poland. [9]

With respect, the fact that you're musically trained will have no relevance if you are wanting a job as a proofreader or English language teacher. My advice would be to contact schools and/or corporate/law firms with a clear vision of how you can be of service and to have done research and preparation. Also you will have to consider the type of contract you wish to be working under - 'temporary' or a proper employment contract. I'm sure this forum has many threads on that. There really is a lot to think about and plan for.

Work / Soon in Warsaw from Budapest. Job opportunities for a musically-trained person and proofreader in Poland. [9]

This might be worth a look: anicecupoftea.pl

Travel / WHAT TO WEAR END OF JUNE FIRST WEEKS OF JULY IN WARSAW [25]

Just seen this post so maybe you've already changed your USD ... If not I would recommend finding a good kantor (exchange bureau) in the city. The ones at the airport offer low rates :-(

I made an iPhone app that shows the National Bank of Poland's daily mid-rate for 48 currencies and lists over 80 kantors in Warsaw.
It's called FX Warsaw, and it's free. HTH.