Fans are spinning at highest RPM after disassembly.

Based on the photos, something is off with the paste. It shouldn't look like it overflowed as in the photos. For example it should not be on the green part of the board. Either you used too much or applied it too thin and incorrectly. Too much paste is actually very bad and can overflow and definitely overheating. Too little paste and manually spread thinly over the chip is also bad. Recommend you remove the paste and start again. First, do not use anything that will cause static electricity. That will kill your parts. Ground yourself with a grounding wrist strap and de-engerize yourself before you touch any electronic parts. Apply absolutely fresh paste to chip. Use no more than a pea size drop. Put drop in middle of chip. Do not spread around. Push thermal sink/fan gently on top of CPU chip so the contact pressure gently disperses the paste. Not every inch of the chip has to be covered. Your fans are kicking on or revolving very high to save your CPU from burning up. The CPU sensors on the logic board are reading high temperatures. Another thing to check is the BIOS and/or firmware version. Update to the latest. Hope this helps. I have been building, fixing, and updating computers for close to 30 years. Good luck!