Unlearn

[Hina Muqadas]

To forget, as what has been learned; to lose from
memory; also, to learn the contrary of.

[Luis Fok]

Context: One attempts to [undertake] a higher-level of learning in a specific [intensive] study course.
However, this intensive study course erases [the foundation] previously obtained in prior elementary courses. This is mainly caused by the retardation of a professor, lack of knowing the national language, or both.

[Tina]

Discard (something learned, especially a bad habit or false or outdated information) from one