I use a Samsung Galaxy Prime which I purchased some months ago from Samsung showroom in Wise, Abuja. Attached is the phone's specifications.

I recently noticed the phone's processing speed had deteriorated. Upon enquiry I discovered the average size of each picture I take is 1MB. Yes, I mean 1MB! Some pictures I take are as large as 2.2 MB. I have checked my camera's setting and I am presently using the lowest resolution. I even had to download another camera but all to no avail.

I also discovered apps I download become larger in size on my phone. For instance, I downloaded Firstmobile which is supposed to be 24 MB but on my phone it's 84. 77 MB!

YouTube is about 38 MB on my phone while the actual size ought to be 16 MB. Whatsapp is 102 MB as against its default size of 23 MB.

I need your kind advice on what to do to resolve this challenge.

It's common with today's smartphone.
Hope you know the app you downloaded was bare, you registered the WhatsApp, added friends, messages are archived, you send and receive files and media messages. All these put together add to its size. As for the camera and photo size the higher the pixel of your camera the bigger the size, the more light captured by your camera the bigger the size. That's why our smartphones have lifespan(software) because after series of updates the memory becomes whack.