Give reasons for which I agree

[ROBINDESBOIS]

or by which agree with the ..............

[Perikles]

We need more context - it makes no sense to me.

[AngelicaDeAlquezar]

I think the original sentence might be something like:
Ahora expondré/diré/expresaré/citaré/enunciaré/daré las razones por las cuales estoy de acuerdo con el gerente.

For which, I'd propose:
Now I will tell the reasons why I agree with the manager.

[Perikles]

I think the original sentence might be something like:
Ahora expondré/diré/expresaré/citaré/enunciaré/daré las razones por las cuales estoy de acuerdo con el gerente.

For which, I'd propose:
Now I will tell the reasons why I agree with the manager.in which case, it would be

Now I will give the reasons why I agree with the manager.

:)

[ROBINDESBOIS]

It sthg like
Today I have to give you some reasons by which I agree or disagree with the following expression................

[Perikles]

It sthg like
Today I have to give you some reasons by which I agree or disagree with the following expression................Today I have to give you some reasons why I agree....

Today, I have to justify why I agree ....
Today, I have to explain why I agree..

[wrholt]

Adding to Perikles fine suggestions:

It sthg like
Today I have to give you some reasons by for which I agree or disagree with the following expression................