I'm also a beginner. What I'm about to write works for me, and was learned by trial and error. If someone else would like to add or correct, please do so.
Well, for example, on a photo like this
, you could have chosen spot metering - but I think you could even have gotten away with medium-center.
Er... both my manual and the camera menu are in portuguese, but you get three choices: matrix, medium-center and spot (I hope that's a correct translation).
Anyway, where were we... OK, select medium-centre metering and set you focus area to the centre of the image. Then point the focus point to the lady's face.
Now, half press the shutter button to get a metering and press the "AE-L AF-L" button. This will lock both the focus and the metering. Keep both buttons pressed and recompose the scene, then shoot. You'll get a correct metering for the lady's face.
You can set the "AE-L AF-L" button to lock either the focus, the metering, or both.
There's a very quick test you can do in your house. Go to a dark room and switch on the ceiling light.
Now, take a photo of the ceiling light as usual. The camera will correctly measure the whole of the frame, thus providing a balance between the lamp and the ceiling. You'll be able to see the lamp, but the ceiling itself will appear very dark. This is "technically correct", but may sometimes be contrary to your intention.
Now, let's try with exposure lock (AE-L). Point to some piece of furniture and press half the shutter button and AE-L. Now recompose and take a photo of the same lamp. This time, the lamp will be very bright (you probably won't be able to tell there's a lamp there, but the ceiling will be very distinguishable (i.e. the camera is being forced to treat the photo as if the light source wasn't there - it's being forced to treat it as if it were of the same brightness as the piece of furniture). This is of course "technically incorrect", but may sometimes provide better results.
Again, you can set the "AF-E AF-L" button to lock only the exposure, so you could be metering on some object and then focus correctly on you subject.
On that particular photo
, using medium-centre metering and exposure lock, would have gotten the lady's skin in a more medium brightness, although the background trees would appear even brighter - but then your subject is the lady, not the trees.
High contrast situations are hard to deal with. You did a great job - with a little room for improvement.