Hello,
1) The marriage with C is null and void and therefore it can not be dissolved but declared Void by a court order. If C is agreeable you can move a petition and get the marriage decreed Void. You may have to pay her a compensation to get her to agree to it.
2) As you have already married B the marriage is still valid and subsisting. You need to get her back with you. Once you have obtained a decree of Nullity of the second marriage, you can file for Restitution of Conjugal rights to get B back.
3) Before you initiate legal steps it is advisable to initiate talks with the parties concerned to get their consensus as you have to deal with two opposing parties who are equally aggrieved.