If you get an error like "insufficient memory", "storage low", or the like, this usually refers to the
/data partition. That is not only where user-installed apps go to, but also their data.
You tried to free some space by deleting "pre-installed apps". They are usually referred to as "system apps", as they reside on the
/system partition. So deleting them usually does not free up space on
/data (to be more precise: it only frees up little, as those apps store their configuration and data there). Which explains why your "delete operations" had not the desired effect.
Following the insufficient-memory tag, you will find a lot of questions dealing with this issue. I heartly recommend you visiting its tag wiki first, which gives you some "first aid". For more information, check the highest frequented questions next. If there are still remaining points, feel free to ask a new question addressing those.
PS: This 3-step of "tag wiki", "tag faq" and "remaining questions" fits in many places. Unfortunately, our tag wikis don't receive the attention they deserve...