Not sure what to do

If not wanting to honor the lease is the only reason the landlord has for refusing to follow it (for example, the landlord doesn't claim fraud, that the lease is illegal in some way, that it gives the landlord the right to terminate it, that the person who signed it for the landlord was not authorizedto sign it, etc.), a court would force the landlord to comply. It is possible that the other tenant has a lease with a restrictive covenant in it, i.e. a provision that says that no bar can occupy your premises.  If so, one of you is going to lose out; it is impossible to comply with both leases.  In that case, if you can't work out a settlement between the 3 of you, the landlord would be liable for any damages the losing party suffers.  My instinct would be that if, in that case, the other party had recorded its lease, it would win, you would not be able to operate your bar, and the landlord would have to pay you any monetary damages you could prove that you had suffered due to its breach of the lease, because you could have discovered the restrictive covenant if you had checked the land records; if the other tenant had not recorded its lease with the restrictive covenant, my sense it that it would lose, you could open your bar, and the landlord would have to compensate the other tenant for the breach of its lease.