Very and too have different meanings. Consider this example:
I have $100.
This bottle of wine costs $90. It's very expensive, but I can buy it.
That bottle of wine costs $150. It's too expensive, so I can't buy it.
"Very" in front of an adjective amplifies it. To amplify something even more than "very," you can say "extremely":
It's 75°F. It's hot.
It's 90°F. It's very hot.
It's 105°F. It's extremely hot.
"Too" means "more than the limit." For example:
You must be 17 years old to watch this movie. Jackson is 14. He's too young.
This shirt is a size large, and I need a size small. The shirt is too big for me.
The train left at 8:00 and we got to the station at 8:30. We arrived too late.
Remember, use too much and too many before nouns... and use too before adjectives. You can't say "The shirt is too much big." - because "big" is an adjective.