Is it normal have dizziness and temporary vision loss during extreme exercise?

This is not normal . But certainly could be attributed to dehydration and electrolyte imbalance. Any eye cause would have to be ruled out by examination.
No. Sounds like you are may be pushing yourself too hard. Be sure to be checked by your primary care physican before embarking on an exercise program to rule out heart or other problems. The dizziness and temporary vision loss usually means your brain isn't receiving enough blood - best to find out why!