"English samsarikkan" probably translates to "improve English" since "samsarikkan" is a colloquial term for making something better. "Oru formula" means "a formula," "PDF free" is self-explanatory, and "13l link" might refer to a 13-lakh (1.3 million) file link, though "13l" could also be a typo. Alternatively, "13l" might be part of the name or version of the resource, but without more context, it's hard to tell.
