According to Google, you asked, "I need your advice, I tried to paint the landscape to make it look more real and never satisfied with the result. Please give advice." If I got it wrong, I apologize, but blame Google. 😁
Some things to try:
Work with rule of thirds. Move horizon to 1/3 of the way from the top or the bottom.
The sandy beach looks more like a mountain. Maybe keep the left end below the water line.
Things look very flat. Give objects (water, blue thing, brown thing, green thing, palm tree, sky/clouds, & sun) texture by adding detail.
Study other paintings of beaches/water/sky. I mean really study them. Enlarge them so you see brush strokes. Then practice what you see.