#Hagar gave birth

Hagar's return to Sarai and Abram is implict. You can make this more explicit: "So Hagar went back and gave birth." (See: [[:en:ta:vol1:translate:figs_explicit]])

#named his son, whom Hagar bore

"named his son by Hagar" or "named his and Hagar's son"

#Abram was

This introduces background information about Abram's age when these things happened. Your language may have a special way to mark background information. (See: [[:en:ta:vol2:translate:writing_background]])

#bore Ishmael to Abram

This means "gave birth to Abram's son, Ishmael." The focus is on Abram having a son.