c # – how to create enterprise level software?

We are a software and application development company based in India. We create software and applications for the automotive sector for companies and dealers such as Suzuki, Toyota, Ford, etc. During this time, we have developed various tools related to CRM, vehicle tracking, taxi applications, sales, their resellers and others as well.
We now want to collaborate with this software and create a set of different applications in a complete system sold online, licensed and by dealer. Need help on how to create this transformation.