Learn Turkish: Nasıl olsa pergeli planlama masasında unutacaksın. - You will forget the compass on the planning desk anyway.

This is a verbal noun purpose compound. It combines the verbal noun planlama (planning, formed by adding -ma to the verb planla-) with masa (desk). To link them, we add the third-person possessive suffix -sı to the second word, creating planlama masası (planning desk). Finally, we add the locative case suffix to mean "on the planning desk."

Why is there an -n- in masasında instead of just adding -da to masası?

When you add a spatial case suffix (like the locative -da / -de) to a word that ends in a third-person possessive suffix (like the -sı in the compound planlama masası), Turkish requires the buffer letter -n- rather than the usual -y-. So it becomes masası + n + da.

Why does pergel take the -i suffix to become pergeli?

The -i is the definite accusative case suffix. Because the speaker is referring to a specific compass ("the compass" rather than just "a compass"), it must take the accusative case to show it is the definite direct object of the verb unutacaksın (you will forget).

Is nasıl olsa a fixed phrase here?