What do you not understand specifically? To expand upon my points though:
I believe that salvation is the beginning and end of discipleship. On one hand, we do not begin being disciples of Christ and growing in Christ likeness until we are saved. On the other hand scripture affirms that we are to work out our own salvation, becoming more like Christ every day. And from another perspective, our salvation was accomplished in Christ through his sacrifice. And from another perspective we do not fully become like Jesus until we see Him face to face on that day. etc. etc. etc. Salvation is like a diamond with many different facets and hughs.
And concerning the Kingdom of God being both now and not yet, it’s a common means of referencing the very present reality of the Kingdom while all the while reconizing that it is not fully seen/understood/experienced yet by us. The kingdom of God is both a present reality and a future hope for us.