Cant see anything through camera

It appears the model has a recall of sorts. Your needs professional repair.

https://www.nikonusa.com/en/service-and-support/service-advisories/coolpix-3100-3500-4500-5000-5400-5700-and-sq-service-advisory.html

https://www.google.com/search?q=Nikon+e5700+cool+pix+service

..

Need Lens unit replace. Send to Nikon service.

If you have changed you media card, that could be the problem.

Not all media cards are the same! Some are faster then others, try up-grading your media card!

Try the procedures in this tip.

i dont think you can do anything you just have to reffer to a proffessional because there are some gears that maybe damaged

One of the advantages of higher-end cameras is speed. You might get a SLIGHT improvement with a higher-speed memory card, but I doubt it.

If you really need to take pictures quickly, you need a different camera.

Remove the battery, wait a couple of minutes, replace battery. (assuming the battery is fully charged. Check there is nothing jammed in the mech. if it still stays stuck.

Try one of or all of the Nikon sites. other than that, get a card reader to read the cf cards directly into pc/image editor.

Get onto Nikon Customer Support this is a main board problem

at the back of the camera next to the view finder (bottom right hand corner) is a button and icon marked SEL. pressing this button toggles the lens image from the view finder to the lcd screen and back again. IF neither view is available then I suspect your camera needs some TLC at a repair shop. hope this helps.