how can i rescue my phone?

[OceanDean]

Hi! I am using samsung a51 at the moment, and I have spotted some weird activity on it..

I have some messengers installed, sometimes, I can see messages from people are already read when I didn`t read em Huh
Also, yesterday my phone just turned off without my action - he just did it by himself.
Also, my battery is discharging too fast - I remember when I just purchased a phone, he could hold the life for 1 day without charging easily!
Now it can`t go for even a 14 hours working day.
Recently found in internet that my phone can be under spy, but I am too newbie in that, what does it mean? When I googled `phone spy apps` I found a couple of articles and websites are offering ALL spy related functions - gps tracking, text spying, call recording and maaany others things for like 2$ dollars (what?) so people instead of making phone defence better for a small amount of money doing spy apps, and charging these money for making phones worth? Where is the logic?
Guys, who can told me how to detect and remove these spy apps from my phone (if they are really installed)?

Thank you guys for any help in advance, I got so many important information on my phone so I don`t wanna drop it or make a full restart, cause in case of full restart I should go for some cloud storage, and this app can jump in it also..

[OceanDean]

Finally, I found the resolution - on this website http://celltrackingapps.com/spy-apps/ I found signs of spy apps and how they act, also the solution is found here ^^