Step 1:
This pink folding paper is about 20x30 centimeters and white on the backside. Fold over the yellow line.

Step 6:
Fold the edges to the centerline.

Step 5:
Prefold in half.

Step 2:
Fold over the left line first.

Step 4:
Prefold over both lines.

Step 3:
Fold over this line

Step 10:
Fold over the yellow line and press the three edges to the right, use tape or glue.

Step 8:
Prefold these lines into the right directions

Step 9:
Fold the three edges upwards, use the prefolded lines as guidance.

Step 7:
Fold the edges to the centerline.
Then unfold the folds of steps 6 and 7

Step 16:
All folding lines are prefolded in step 12

Step 15:
Press the edge downwards over the prefolded lines.

Step 12:
(Pre)Fold all eight parts downwards, see arrow as example.

Step 11:
Turn the model.

Step 14:
Glue both edges together, see arrow

Step 13:
This is how the prefolded bottom of the cup should look now.

Step 19:
Press / fold the edge downwards on two more spots, see arrows as example.

Step 20:
Valley-fold over the two short yellow lines and bend / curve the top downwards.

Step 18:
Press / fold this spot downwards.

Step 17:
This is how the bottom of the cup should look.