This is the 800th most frequent Bulgarian word.
със
The Bulgarian word "със" means "with" in English.
The word 'със' here is used as the word 'with' and is paired with 'сестра си' to indicate companionship.
Аз отивам със сестра си на кино.
I am going to the cinema with my sister.
In this sentence, 'със' functions similarly to 'with,' here paired with 'старата техника' to describe the means or tool used to complete the project.
Направихме проекта със старата техника.
We completed the project with the old equipment.
Here, 'със' implies the manner or quality of the action and is used with 'сериозност' to express the approach or attitude towards the problem.