Learn Portuguese (Portugal): Medimos esta peça depois de cortar o material. - We measure this part after cutting the material.

In Portuguese, when a verb comes right after a preposition like de, you must use the infinitive (the basic, unconjugated form of the verb). So, for 'after cutting,' you use depois de followed by cortar. Portuguese doesn't use its '-ing' equivalent here!

Is medimos in the present tense or the past tense?

It can be either! For regular verbs ending in '-ir' like medir (to measure), the nós (we) form is exactly the same in both the present tense ('we measure') and the simple past tense ('we measured'). You have to rely on context to know which one is meant.

Could I just say depois cortar without the de?

No, the phrase for 'after' when followed by another action or a noun is always depois de. Without the de, depois just means 'afterwards' or 'later,' as in medimos depois (we will measure it later).

Why is it esta peça instead of este peça?

The word peça (meaning a part or piece) is a feminine noun. Because of this, the word for 'this' must also be feminine, which is esta. If you were talking about a masculine noun like material, you would use este.