Need some help with diagnosing my car. Young guy learning

I agree with RRR, youve got a bad primary connection someplace. also check that your batt cables are tight, not corroded, broken, etc and neg cable has a good, solid ground. Its a tedious process, but if you have to go thru each connection 1 at a time, sometimes thats the only way. an afternoon with a brass wire brush & WD40 can do wonders.