Hi Neoma,
Sounds like you've got a bit of good news! Your camera and lenses are working as they should, no repairs or replacements needed.
The next step is to begin to learn more about the craft of photography.
Here's a video that will help explain how metering works with dSLRs. After watching a few videos, I think this one is the most beginner friendly.
But, be aware that when the presenter in the video talks about "partial metering" he's discussing a metering mode that Pentax cameras do not have.
The rest, however, is right on the money.
If you still have any questions, feel free to ask about it here on the forums.
While I agree with other posters in this thread that newer lenses can make your new camera really sing, I would first suggest that you work on improving your own knowledge and skills before shelling out lots of cash on gear! Without first developing the fundamentals, you'll not see dramatic improvements in the quality of the photos you take.
(Plus, if you fall in love with photography like the rest of us here, you'll have plenty of time to buy more equipment!)
In the meantime, it sounds like you're beginning to take your first steps toward taking your photographic work more seriously. I hope your journey in photography brings you as much joy as it has for me!
All the best,