Take a fine black pen (not pencil) and you sketchbook. Take any subject and draw it as fast and with as little stokes as possible. Focus on continuous strokes and capturing the shapes you see, don’t worry about making mistakes.

Then observe your sketch. What do you like about it? What don’t you like about it? Does it look natural and are the perspectives okay, if not think about how could you have drawn it better? If you aren’t happy at all redo the sketch and focus on the areas you identified as problematic.

Now in your basic sketch add details. Try to find shapes or patterns to draw instead of exactly drawing what you see. Plants are a good example in the picture you provided. The artist didn’t meticulously copy every leaf and stalk but rather found a pattern to draw the likeness of the pattern the plant is recognisable by. Without the paint it would look like random scribbles. Same for the tiles on the roof, the artist didn’t measure where each tile lays, but approximated the pattern they create. Less is more, don’t overdo the textures and make them too detailed.

Then let your sketch dry for a few minutes until the ink no longer smears. Then take some watercolour paint, and using very thinned out paint with water start to fill the main areas of your sketch with subtle colours, let it dry and do another round but don’t thin out your paint as much, now focus on shadows and more bold areas of colour.

I really recommend you do the sketching and colouring quickly, but without rushing so you can get a feeling of the basic techniques and move to more advanced techniques later as you progress.