There is no 'fully mine a block', each hash is random and each hash has a specific probability of finding a block.

It's purely random luck statistics for every single block mined.

Same as rolling a dice - how often you roll the dice determines how often you 'expect' to get a 6.
But anyone can roll a 6 on the first try (1 in 6 chance)

Just with bitcoin the numbers are ridiculously much larger.
Firstly, the dice has 2^256 sides (~10^77 or getting close to the number of atoms in the universe)
There's also a number of the sides that count as a block (currently a little more than 8^19 or 9.0x10^22)

So it boils down to probability, not 'yes or no'.

So e.g. a 90TH/s miner currently has an approximately 1 in 11625 chance of finding a block in a full day of mining.
So that leads to: 9TH/s is 1 in 116250 ... etc.