When the first time use, the game surely is fast (if not mistaken 2 years ago). Lol. But as of today, the game a little bit slow when open the game (loading) compare to Ip.. or a S series. But i am still good with it because the loading is not my main priority. Beside that I do use Samsung J4 (2018) for Pokemon Go too. To me, it just like a bit slow only. Not much issue.
The only thing I can say is for A51, other than slow on landing page, next one is battery issue. It drains quite fast. Still manageable. Lol