Learn French: Il mène temporairement le projet pour un semestre. - He is temporarily leading the project for a semester.

The preposition pour is used to express a projected or intended duration, usually looking ahead from the present into the future. If the action were completely in the past or just a general statement of elapsed time, you would use pendant. Since he is taking on the role for an intended duration starting now, pour is the right choice.

Since pour un semestre implies a future duration, why is the verb mène in the present tense?

In French, the present tense is frequently used for actions that are happening right now and will continue into the projected future. The phrase pour un semestre sets the timeline, so the present tense mène perfectly translates to 'he is leading' in English.

Why does mène have a grave accent (è) when the infinitive mener does not?

Mener is a stem-changing verb. When the ending of the conjugated verb is silent (like the -e in the il form), the e in the stem changes to è so the syllable can be stressed and pronounced clearly. You see this same pattern in verbs like acheter and peser.

Could I put temporairement at the end of the sentence instead?