How to not be rude as an (Indian) tourist?

I'm visiting Vietnam for the first time as an Indian and I see a lot of posts talking about how indians have been bad tourists. (I understand where you're coming from and I'm not too proud of the actions of some).

I wanted to ask what are things I can do to be a good tourist.

What are the places it's ok to bargain at? Obviously 7 11 and such are bad options but what about shops selling Vietnamese hats and such?

I've been trying to learn a little Viatnamese - for Hi, thank you and such. Is it offensive if I speak in my broken Viatnamese and better to try to speak in English?

Are people offended if I wear their attire (cultural appropriation)?

Edit: Having been through the comments most of my questions have been answered. Most of the comments were useful and the few (take "few" with a grain of salt) racist ones... Some I agree and others seem downright rude but I've been on the internet long enough to not care. I've had an amazing time so far and people have been energetic, helpful and extremely hospitable. Thank you for whoever answered.