I mean what do expect of samsung galaxy a11 phone after all ? its just using Qualcomm SDM450 Snapdragon 450 and its old enough to lagging, but after all i suggest you to use SD Maid app, to clear cashe the phone and its so easy to use and have lots of features to use! and if you can download the pro version of it , its so much useful than the free version. if you lagging or have problem with it after clearing the cashe and do what i said to do, you can get backup of your phone and factory reset it and use it again like new :)
Hope this helps