I am planning to stay in a hotel for first 1-2 weeks so I can search a flat. Any hotel suggestion ?
Find one which is close enough to your work place - use zumi.pl, example:
click point A, B... in the left menu and you will see addional info - like hotel web page, phone number and so on
While I am searching a flat to rent ? Will I need someone who is native to Polish ?
Yes if you want to find good flat for reasonable price