Heyyyoo friendos!

Another hospitable Vietnamese, i get to say you guys are far more friendly than I have been told. Damn those Chinese people who said you are hostile!

By the way, is there any big bookshop around Dis.5 or 1? I need books to learn vietnamese.

Haha glad you get to see for yourself our hospitality! I've heard my foreign friends said they thought we don't speak English much either. But that is also wrong, talk to a young folk on the street, 8/10 times I'm sure they can communicate with you in English!

Oh there are many bookstores in District 1 and 5... Biggest and most common ones must be those FAHASA book stores. You can go to their website fahasa.com. But there's one very near to Ben Thanh market
There's one I really like on Dong Khoi street near Vincom center too. Arg can't remember its name but it's a green and white store, and you'll see it on the left if you walk from the Notre Dame Catheral toward Vincom.
There's Phuong Nam bookshop, it's a huge store, they have table and seats, I think they serve some drinks too so you can sit and read there if you dont' want to buy.  Pretty amazing. It's on 2A Le Duan street. Yeah so just walk down Le Duan street from Diamond plaza and you'll see it on the left.
So those are some! They all have lots of book specifically in self teaching Vietnamese for foreigners! Oh and if you don't mind used, old books on random topics, can always walk around the backpacker streets and you'll see plenty of small bookshops.
Hope this helps!