FYI Adobe Lightroom will compress the pics but still keep best possible resolution. There are other tools but this one is straightforward to use and the full version is free for 30 days. I’m a creative photographer and use it all the time.
To change picture size - import pics first. Then select pics to change, click Export (bottom left corner) and under File Settings / Limit File Size To, put in the size you want. You can also clean up the white balance and tone to take out that yellow tint.