Replying to [Made in Vietnam] concerning your 3 questions:
1. Start with identifying exactly what products you want to sell to exactly what target market. You'll go broke unless you firstly identify your buyers under exhaustive marketing research.
2. Suppliers don't give two hoots about your background. They are happy to sell you whatever you want (and don't want) the same as the shop around the corner from your home. But, you'll likely come a cropper unless you also do exhaustive due diligence on potential suppliers.
3. Yes, Vietnam is making great leaps forward in being a reliable supplier of many sorts of products at a very competitive price. But, dud goods and scammers also exist there same as in any country on this planet.