To do can simply replaced by the verb Faire – The translation

I don’t like to exercise but I do

Is translated to

Je n’aime pas faire des exercices mais je le fais (quand même)

And

I hope he learns Esperanto but I don’t think he will

Is translated to

J’espère qu’il apprend l’Esperanto mais je ne pense pas qu’il le fera

In the above example you cann see that you just have to literally translate the verb do with the same tens

In French you can in most cases use faire to replace any other action implied by the context, but you’ll also need to refer to the action with a pronoun (le).

Je n’aime pas m’entrainer, mais je le fais quand même.

J’aimerais qu’il apprenne l’espéranto, mais je ne crois pas qu’il le fera.

Note that you can naturally express tense, but if you also want to express modality (should, could, etc.), in most cases, you should use a different phrasing.