Learn Arabic (Modern Standard): كانت نحلة قد لدغت يوسف أمس.

The past perfect ('had done something') is formed by combining the past tense of كان (to be), the particle قد, and the past tense of the main verb. Here, كانت plus قد plus لدغت translates to 'had stung'.

Why are both كانت and لدغت in the feminine form?

Arabic verbs must agree with their subject in gender. Because the subject نحلة (a bee) is grammatically feminine, both the helping verb كانت and the main action verb لدغت must take the feminine past-tense suffix.

Why is the subject نحلة placed between كانت and قد?

In Arabic verbal sentences, the subject normally follows the first verb. Since the helping verb كانت acts as the main structural verb of the sentence, the subject نحلة comes immediately after it, right before the second part of the verb phrase (قد لدغت).

Why doesn't the name يوسف take a double vowel (tanween) at the end like most indefinite nouns?

يوسف is a foreign name in Arabic, which places it in a special category of words called 'diptotes' that never take tanween. Even though it is the direct object here and takes a fatha sound, it is just pronounced 'Yusufa', never 'Yusufan'.