I’m a foreigner (european)
see my comment:
The yuanta App "投資先生"is quite overloaded and has 1000 features. I only use one (buy ETFs).
Also it’s only in chinese. So it was quite complicated to get the hang of it in the beginning. But if you know where to look it is easy 
The staff at the tianmu branch is very helpful and can show you everything you need.
Also beware, that normal trades are in units of a 1000 shares.
So buying 1 unit (= 1000 shares) of the yuanta etf. Currently trading at 58 TWD = 58.000 TWD
There is a special option to buy a fraction (less then 1000) in the settings.