Welcome to the communities :smileyhappy:
For VCP exam's you need to attend a training which will be of 5 days - > VMware NSX: Install, Configure, Manage [V6.2] . vSphere knowledge is must and i would always suggest a VCP6-DCV training rather than associate level training.It is hard to say how much time it would take to learn and be confident,because practical knowledge really matters and one should at least do few installation and break fix to understand head and tail on various features and their functionalities .VMware HOL labs are great place if you don't have the feasibility of building the labs.
VMware Learning Platform
Also do check - > Public Resources for Customer and Partners to learn NSX
As far as NSX VCAP exams , first and foremost go through the exam blueprint few times VCAP6-NV Deploy Certification Exam . R&S knowledge is good but most importantly Never skip any tasks in blue print - These are lab exams with scenario based questions so you should practice a lot and i will recommend building a small lab and leverage HOL labs for any extensive feature testing .
Happy learning and all the best for the exams !