These problems have become more serious because of the government have failed to end corruption.

Ok, so there’s a problem here because of ‘because of’!

It should read:

• These problems have become more serious because the government have failed to end corruption.

Just follow this rule:

• because + cause sentence
• because of + cause noun

If you really want to use because of then you might write:

• These problems have become more serious because of the government’s failure to end corruption.