My iPad keeps crashing. - iPad Apple Tablets & eReaders

if the hard drive is the fault , any computer / IT repair shop can fit a new one

You could turn off and turn on your iPad and then try again.
If that doesn't work then uninstall the app and reinstall.

That's because it's simply not powerful enough to handle ios8. I know apple gave the update but unless they give a new bug fixing update to fix the crashing, your stuck with ios8 and a crashing iPad.
I have my iPad 2 with ios7 and I'm not planning to update it.

when you mean reboot, does safari crash and goes back to the main screen?

Try reinstalling it.

Uninstall some unused apps and clear space.

It appears the app you are using is crashing. Try deleting it and re-installing it.

Safari is junkola, get Chrome or another browser. Safari always has issues with mine.

Try to update it (if possible)

Close unused tabs

Tap Settings in your Home screen then tap Safari / Clear History, Cookies, and Cache.

Then restart your iPad. Press and hold the Sleep/Wake button until the red slider appears. Slide your finger across the slider to turn off iPad. To turn iPad back on, press and hold the Sleep/Wake until the Apple logo appears.