I presume that with every missed payment, the interest amount due that month goes onto your mortgage?
Yes, if you owe €100,000 at the start of Month 1 and the interest rate is 5% and you don't pay it, you will owe an extra €416 at the end of month 1. At the end of month 3, if you pay nothing, you will owe around €101,250.
If you pay €416 per month, you will owe €100,000
If you pay €1,000 per month, you will owe €98,250
If you have rental income in the tax year, there is an advantage in paying the interest. You will be able to deduct 75% of it when calculating your taxable income.
Brendan