Learn Finnish: Hän poseeraa minun edessäni, koska pituus on ongelma. - He poses in front of me, because the height is a problem.

In Finnish, when a postposition is used with a personal pronoun (like minun, meaning 'my' or 'of me'), the postposition must take a matching possessive suffix. Because it goes with the first-person pronoun minun, we add the first-person suffix -ni to the postposition, resulting in minun edessäni (in front of me).

Is it possible to drop the word minun from this sentence?

Yes! Because the possessive suffix -ni on edessäni already makes it perfectly clear that it means 'in front of me', the pronoun minun is optional in standard Finnish. Saying Hän poseeraa edessäni is completely correct and very common.

Does the postposition edessä contain the -ssä (in) ending?

Spot on! Edessä comes from the root word etu (front) combined with the inessive ending -ssä (in). So it literally translates to 'in the front', and minun edessäni literally translates to 'in my front'.

Does pituus only mean 'height'?

Pituus translates to both 'length' and 'height'. It is created by taking the adjective pitkä (which means either 'long' or 'tall') and adding the noun-forming ending -uus. When talking about people, pituus is the standard word for someone's height.