how can i develop my skill on photoshop

Practice, Practice, Practice, Learn New Techniques.

Even the Photoshop Masters and other ACPs will tell you then never stop learning.  There is always something new to learn with Photoshop.

Adobe Generation Professional / the Adobe Education Exchange event offers FREE courses!

You can also watch videos on YouTube.... or watch the Adobe channel on Twitch!

Then also pick up magazines like Imagine FX, Computer Arts, etc.  Attend events.... meet other artists and ask about their techniques!

You will continue to grow with this program... it is great and learning is something we continue to do!

On YouTube there are some very good clips, but also the worst ones. The same with web sites offering tips and tricks. If you want to be sure to have quality information, stay on Adobe for any free information. I often start with Adobe help for specific problems.

There are "Classroom in a book" books.

And there is the Lynda.com (or linkedin learning, they are the same). There is also Vide2Brain for courses in Spanish, German or French.

A good idea (for amateurs) is also to look for a photographers club. They offer quite often courses and seminars on specific themes, even that the quality of those courses are not always at a higher level.

You get what you pay... :-)

Specific questions get answerers here! Don't be shy.

If you live in or near a large city, I suggest you check the Adult Ed (also called Continuing Education) courses that may be available at a nearby college, the local Y or community center. Check their sites to see course descriptions. These classes usually provide the opportunity to work at a computer as you cover the material, proceed in a logical sequence and ask questions during each session. Some instructors offer email assistance when an assignment has you baffled.  In addition, you will meet people with a similar interest and probably form a mutual-aid network when the class is over. Avoid the One Day cram courses. They are worthless for a beginner. (The courses I taught at a college in NY met for three hours on 8 consecutive Saturday mornings and was limited to 15 students. I suspect other colleges have a similar setup.)

Perhaps the best (and most expensive) training is personal training, typically: Adobe Classes & Training Denver - Adobe Online and Onsite

This link is an excellent place to start:

Adobe Photoshop Learn & Support

Note the links to both the User Guide and free Tutorials.

If you follow the Tutorials link, you will find lots of free videos to get you started. if you budget allows, you might also look for Adobe Certified Instructors in your area and sign up for a class, which is the quickest way to get you up and running.

~Barb

There are some very good books such as the QuickStart Guides and Lynda.com has excellent online video tutorials, such as: Photoshop CC 2018 Essential Training: Design  (you can get a 30-day free trial), and of course you can ask specific questions on this friendly forum.