1. Usage of doubt / denial verbs with imperfect subjunctive mood

2. Imperfect subjunctive - usage
Doubt and Denial
When constructing a sentence, put the denial or the doubt statement in the first part of the sentence in the past tense (must be imperfect to be a doubt), use que, and then put the second verb in the past subjunctive. DOES NOT NEED CHANGE OF SUBJECT.

3. Doubt/denial verbs dudar-to doubt
no pensar-to not think (e to ie stem changer)
no creer-to not believe
no estar segura(o)-to not be sure
negar-to deny (e to ie stem changer)
hay duda-there is doubt
¿creer?-do you believe?
¿pensar?-do you think?

4. Dudaba que tú comprendieras esta lección en italiano.
Examples
Dudaba que tú comprendieras esta lección en italiano.
I doubted that you understood this lesson in Italian.
No creía que ellos llamaran a nosotros más tarde.
I did not believe that they called us
very late.