I have a late 2009 iMac running OS X 10.11.6. I took a Mac update and it messed up everything. Did a clean install using the original disks then updated back up to 10.11.6 but my machine is now running so sluggish. It was fine before this mess started. Now 2 out 5 times the screen freezes on the apple logo and I get all this text that is too fast to read? I have included some screen shots. I would be very thankful for any advice.