Hello, everyone.
I’m having some trouble doing a mesh for this part of my college project.
It is a rounded shaped bag with those details you can see on the following image.
How can I model this? Do I use a modifier after doing a cube/cylinder-based-mesh? Some edge loops? Curves?
Thank you for your attention! I would be glad if you help! =)
It is hard to tell the shape of your bag with the single line drawing. Can you supply some more drawings of it?
Agreed, I can’t make out the shape of the bag from that drawing. You should post a reference image or a more detailed drawing if we are to help you. I’m just talking for myself tho, maybe someone else will be able to see the bag in that.
I’m guessing a sort of a hand bag? 
I got the impression it was something closer to this “Baggu” brand bag, but OP should be able to take the ideas used and apply them to different shapes.
This bag is mostly a rectangular box, so that’s what we start with, and a loop cut where the handles start.
Then a loop cut along the side, then adjust the edges at the top to make the top of the handle.
Inset faces (your thickness and depth may vary for the scale of your own model) for the part where the sides bend inward.
Add some loop cuts to the handle area so we can bend them inward, and then delete the center faces.
Using Proportional Editing, select the top of the handle and rotate / drag the handles in a bit for a natural collapse, and add a loop cut underneath the handles, and adjust the vertices of the open section to be more of a curve.
Now we make an adjustment to the topology here for a smooth face loop along the curved opening.
Add a loop cut on both sides of the center edge and at the bottom, and arrange the vertices under the opening to be smoother and more curve-like.
Now we make the holes in the handles. In this area, pull the middle vertex at the bottom downward to better approximate a curve, select the 3 vertices at the top of the area made from the earlier inset if they’re a little close and use the relax function to make them less tight, then select the faces that make up this area and inset again, bringing it inward just a little bit. This will be the border of the handle’s hole.
Now we select all the edges that make up the shape’s edges, any place that should have rigid corners, and give them an edge bevel weight of 1.
Add these modifiers, your own thickness / width may need to be different depending on scale, to give the back thickness, more edge loops at the edges, and then a smoother shape. You may have to go in to edit mode and adjust the edge weights of some parts. When I made this I had to make the edge weights at the bag opening smaller due to the thickness of the material there limiting the size of the bevel if clamp overlap was enabled, so I disabled it and lowered the edge bevel weight in that area until the bevel stopped overlapping.
And my final result. You should be able to improve on it a lot and even add more edge loops to the holding section of the bag to make it balloon outward if you like.
@torridgristle I believe you are right on what bag type it is. You should sign up for decryption of images 
You nailed it (or bagged it)
