Life In 19x19

No problem; this is a good move.
Especially at these levels, o16 or s2w's R14 -- both are OK.
But I prefer the original o16, 1-space jump -- good move.
This is not a problem at all. You didn't lose the game here.
Your big mistakes are elsewhere (see below).

OK. W played strangely here. B has a few good options. 3-3 at R17 also possible.
You just want to make sure W suffers here.

Trying to be fancy; greedy. Just connect solidly -- the result is already very good for B,
because W played strangely here. Just make sure W suffers.
I'm sure you did not read out what would happen if W pushed and cut.
You did not consider the results. Which means you were gambling here.

Now you have 2 cuts. You did not read either of them.

Now you have 3 cuts.

This looks like a vital point, but does not actually work.
You have many cuts.

Did you have a plan when W runs ( ) ? ( No. )

Push solidly at D3.

This cut makes no sense. You did not think about the ladder.

This makes no sense. You did not think about the ladder.

This cut makes no sense.

, Terrible. Very bad shape for Black.
Please see Toothpaste .

End of notes.

DiogoBarbosa, may I ask how many games have you finished in your entire Go career -- rough estimate ?