Imi, you can use the lever to lift manually, it's no problem (or at least it shouldn't be). To turn off the auto presser lift you...well, just don't use it
I'm kidding, but it's actually very simple. When you turn on the machine, just press the foot down button and then lift the presser foot with the lever. That will switch to manual mode (it does make a sound, but it's normal, don't worry about it). I find it an awesome feature tho, as it allows me to use both hands to position the fabric underneath.
If you use the pivot function, make sure the option to stop with the needle down is activated, otherwise it's very frustrating (not sure how the menu is on the S7, but this option is in the Sewing Settings which you access by pressing the wrench key on the right of the screen).
You can buy several feet for the walking foot, including a open toe and a 1/4 inch seam.
If you need any help, just send me a message and I'll troubleshoot you through it
Also...might be a stupid question, but did you read the manual? I had several "oooohhh!!" moments when I did.