Some apps stop automatically Android 7.0

[Vinoddivakar]

Some apps stop automatically Android 7.0 How to keep apps active n workin?
Hi I am using android 7.0, n I am having some apps like nqVault, touch protector, automatic call recorder.. which worked fine when I installed them but they stopped working after sometime... They started working fine again when I open them once.. but again after few hours... They stop working again
Automatic call recorder stop recording calls after few hours... Start recording calls again when I open the app once....but again stops after few hours... Same is the case with vault and screen protector
How to keep apps active in background all the time..