What is it that you’re trying to measure?
-8.8dBV is around 1Vpp so the first picture looks correct.
The yellow sine wave in picture 2 and beyond looks distorted, try to increase the time/div without decreasing the sample rate (10ms/div is down to 50MSa/s ? Does the scope have more than 7.5Mpts of memory?)
EDIT: I saw the spec sheet mention that the sample rate is shared by all channels. Disable all except for the one you’re using to maximize the sample rate (1GSa/s * 12 div * 1ms = 12Mpts memory)