Manozac2000

The underlying "sketch" is too dark, and continuous. Make the sketch faint, like the lightest touches of a pencil.

@Manozac2000
Would it be a good idea to remove the drawing lines around the mountains, the drawing lines around the yacht and the drawing lines around the reflection in the lake from the final image?
Having said that, at my present level of skill, I cannot produce anything like as good as what you have produced.
William
 

Also, I like the way that you have done that shimmering reflection.
William
 

A valiant effort, it's tough to make suggestions and not change the style of the painter but a few tips maybe
Improvements:
There is no reflection of the hills in the water, adding these would connect the land to the water. Water glisten if its choppy, it generally doesn't have swathes of white, this also disconnects the boat from the water and the reflection of the boat doesn't make sense.  The sky, it looks like you have made a classic mistake and tried to paint clouds with blue, hence the big block of white that really should be a gradient of colours. The sky is seldom one colour. Tips:
Before you paint really study the subject you want to paint, even when painting from a mental construct (an idea) the reference is from real world experience, whether you are observing a photo, another painting or actually being at the scene, take it in, the textures, the sounds, the smells, the colours. We generally disregard a lot of what we see and we need to stop and really see what is in front of us. Blur your vision or hold up some translucent paper to see the blocks of the scene. Take reference images that you can refer to later on. Paint the things you connect with, this makes painting easier because the desire to paint that subject is stronger. Never rush unless you are trying to do things like 5 min sketches, if its not working don't try and force it. Never be afraid to copy or trace, how else do you get a feel for the form.

this is my third painting... I want to know what changes I must have to draw well

this is my third painting... I want to know what changes I must have to draw well

this looks really cool!

Excellent work!

this is my first digital painting on affinity designer...

this is my first digital painting on affinity designer...

this is my first digital painting on affinity designer...

this is my first digital painting on affinity designer...

this is my first digital painting on affinity designer...

this is my first digital painting on affinity designer...

I must say that I don't miss Adobe at all. Kudos Affinity on creating great design tools!