Hello I just joined plone community I want to contribute to plone .
I knwo htm css javascript shell scripting and python
please help
Welcome to Plone community!
Knowing those things is certainly useful but you need to understand the workflow of Plone first.
Install the Plone locally, you may find this article useful https://docs.plone.org/4/en/manage/installing/installation.html
Play with it a little bit.
Once you know that, you can start with this guide https://training.plone.org/5/
and whenever you feel struck come and post your problem.
This way you'll help us to improve the guide.( also a way to contribute)
If you're comfortable with that pick any issue from the GitHub and search for easy label issues.
For example https://github.com/plone/Products.CMFPlone/labels/41%20lvl%3A%20easy
but remeber to sign the agrrement first before making any PR.
https://docs.plone.org/develop/coredev/docs/agreement.html
good luck!