The B7 chord is commonly used in blues and other genres and is an important chord to have in your guitar chord repertoire. Then study the manual "How to Play a B7 Chord on Guitar: 3 Positions Explained"
play-guitars.com/play-b7-chord-on-guitar/ . With practice, your fingers will become more accustomed to the finger positions, and you'll be able to transition to and from the B7 chord smoothly in your playing.