Work / VISA FOR POLAND AFTER JOB OFFER [2]

Hi everyone,
I recently received an offer from Polish company and they have sent me a Promise letter which states that i will sign the contract in poland.

I have following queries regarding the Next steps:
1) Which visa shoud i apply for , if work visa do I have to have the work permit copy with me or promise letter would be sufficient.

2) Can I get a tourist visa and join the company there after reaching poland and apply for work visa from there only.
3) It would be really great if someone can guide me how the visa process would be like and what documents would be needed ?
4) average time to get the visa ?
5) Is it a possibility I wont get visa even when the Company has promised the job and have obtained the work permit for me ?

Looking eagerly for these answers !!