Hi, thanks a lot for the answers!! They were great! Yeah, I was forcing, blowing downwards, because I was rolling my bottom lip. About this quote:

One thing you could try would be doing some chromatic scales from C# to F# followed by some harmonic slurs and observing how the lips move ever so slightly each half step. Or you could try doing gradually increasing intervals (i.e. C# to D, then C# to D#, C# to E, etc.), but make sure you’re using steady air (ideally Passively released air).

This is spot on! Yesterday I did something like this, I started at C and went up with D – E – F – G (I learned the fingering from an open video from Greg) and I noticed that when I got to open G I hadn’t rolled my bottom lip. Going up like this is an interesting exercise because you naturally change the shape and since you do it in small steps it’s natural, so when you get to G you naturally and gradually made the change in shape. To slur from C do G (or C# to F# for the Singing C) is difficult for a beginner, but today I’m going to do my best and try only to move the corners, jaw and tongue.