Issachar is a strong donkey
Jacob speaks about Issachar and his descendants as if they are a donkey. This emphasizes that they will work very hard. AT: "The descendants of Issachar will be like a strong donkey" (See: rc://en/ta/man/translate/figs-metaphor)
Often in prophecy events that will happen in the future are described as something that is already happening. This emphasizes that the event will certainly happen. It can be stated in the future tense. AT: "Issachar will be" or "The descendants of Issachar will be"
Issachar ... He sees ... He will
Here "Issachar" is a metonym that stands for his descendants. AT: "The descendants of Issachar ... They see ... They will" (See: rc://en/ta/man/translate/figs-metonymy)
lying down between the sheepfolds
Possible meanings are 1) "lying down between the packs they were carrying" or 2) "lying down between two sheep pens." Either way, Jacob speaks about Issachar's descendants as if they are donkeys that have worked hard and are lying down to rest. (See: rc://en/ta/man/translate/figs-metaphor)
a good resting place and the pleasant land
"a resting place that is good and that the land is pleasant"
He will bend his shoulder to the burden
The phrase "bend his shoulder to the burden" is a way of saying "work very hard to carry the load" (See: rc://en/ta/man/translate/figs-idiom)
become a servant for the task
"will work for others as slaves"