Visiting cluj, some doubts

Hi, I will be staying in cluj for around 5 days alone in a few days. What can I do/see around the city? What are some nice places to eat? Can I pay in euros? Is it viable to get Romanian Lei through ATMs? Or should I exchange my euros before I visit? Can I pay with credit card everywhere? How's the average english level over there? How's the public transport? How's the summer heat over there?

I plan to visit both cathedrals, the botanical garden and salina turda, after that, I won't be able to leave the city.

Thanks in advance.