here are some things you can do to get your ace to lag less. http://blog.laptopmag.com/speed-up-an... But honestly that phone in general is pretty slow and buggy. I recommend upgrading as soon as possible to a moto g (free on tab s) or a higher end device if you want. You have to pay off your remaining tab before you can upgrade.
Agree with the above. I had the ace 2x for a year before getting a nexus 5. The ace 2x is just a really low end phone that will lag and freeze at time. If you want a cheap phone today, the moto G is a great choice and will blow the ace 2x out of the water. The two phones will be like a night and day difference.