Hi! I need some help which tools and how I can create a twig that is thick at the bottom and that gets narrow and narrow the higher it get. I also would like to bend or create circular shapes with the twigs with miner twigs with leafs. I found some inspiration on this website: http://www.guymarcal.com/ What I'm looking to create is something similar like the organic shape to the left of the upper image.

Tips and help is preciated! Thanks!

Quick answer: use the Bezier Tool.
When you set the Shape to Triangle, you can create a path and then use the Node Tool on the pink node that will appear. With this node you can change the width of the triangular base.

For the organic spirals, you can use the Bezier Tool as well, but you have to set the Mode to Spiro.
When you have created your path with several nodes, you select them all and convert them to Auto-Smooth, this will magically transform the path into silky smooth curves.

You can also use LPE's like' Power Stroke' or 'Bend' for some effects.

Do a search on youtube for 'inkscape flourishes' and you'll find loads of information on this effect.

You can use pattern along path too with custom shapes, like these.
Example made with spiro lpe.

Lazur URH wrote:Example made with spiro lpe.

Nice result !

How did you create the skeleton path ? Is it a spiro path rotated and gradually shortened ?

Made one spiro path, and edited the nodes manually.
Duplicated it, adjusted nodes so the strokes seemed somewhat "parallel".
Once there was five, used them together to place here and there.

It's not that "accurate", as I think it would look with a brush a bit different -but using a brush and paint wouldn't be accurate in geometric means anyway.

Thanks for the help! I found what I was looking for when I searched for 'inkscape flourishes'. I also discovered that it was easier to use the pencil tool instead of the bezier tool.