Very = 很

When we use very, it's not clear whether what we are describing is a good or a bad thing.

当我们用 “very” 时，并没有说明所描述的事物是好是坏。

The building is very old.

This could be a good thing: 'the building is old and beautiful'. It could also be a bad thing: 'the building is old and falling down'.

这可能是好事：“这幢楼古老而美丽”。也可能是坏事：“这幢楼很老，就要塌了”。

Too = 过于、太

When we use too, it means there's a problem.

当我们用 “too” 时，意味着所描述的事情有问题。

The building is too old.

This is a bad thing. The building is too old. It might fall down and could be dangerous.

这暗示楼很 “古老” 是件坏事。这幢楼太旧了。它可能会坍塌，很危险。