Despite the low specs of this device I have found it is perfectly useable if you do the following.
Reduce the number of background apps running to 2 (developer options)
Remove all but the essentials from the Background Activity Manager white list (battery settings)
Install forcedoze and enable it over ADB.
Some of the less essential apps take a while to open but the essentials are fine.
C10 is a mostly obsolete rating for SD cards, in the context of modern devices. If that's the only rating on the card, it will very likely be slowing performance of apps on the card. What you really need is an A1 rated card (ideally A1 U3 V30, but you can get away with a good A1 U1 if you don't want best performance).