I assume from the 2:1 aspect ratio that this is meant to be in Plate Carree projection. That should produce significant distortion of the polar regions which your map doesn't show. The two small continents in the north should be stretched out east to west. Since they aren't, it means the "real" shape on the globe is pinched in toward the poles.
Here's what it looks like in a polar stereographic projection which shows the pinching.
Plate Carree is simple and convenient for data that is going to be reprojected, but it's not a very good choice for a finished map.
Your coastlines are also a bit consistent. If you look at Earth, you'll see that the degree of "crinkleyness" varies. There are smooth areas like the Atlantic coasts of Africa and South America, and there are massively complex areas, like Southeast Asia or Scandinavia.
You do have a bit of a divergent boundary thing going with the two larger continents that resembles the Atlantic basin. That's good. The west coast of the big one looks like it fits with the east coast of the smaller one. I'd suggest you play that up by not running any tall, young mountains along those coastlines. Old rounded ones like the Appalachians (Which run along the east coast of the United states) would fit though.
You're also rather lacking in islands. There are a exceptions, but in general, most major islands are found along convergent boundaries, along with young mountains. Such islands essentially are just mountains or mountain ranges that are partly underwater (Japan, the Philippines, Indonesia, Vancouver Island), while the other kind like are essentially partly flooded plateaus (Great Britain, Greenland, the Canadian Arctic), or mountains in odd places (Hawaii, Iceland).
Thank you for the help Hai-Etlik
The projection is Plate Carree but the continents are not disorted, so I probably need a new projection where I could work without the distortion, if you have any idea
Is there a way to know where the coastline should be more complex or more smooth?
Also, I have some island chains in mind but I dont really know how to draw them so I will add them later.
Also, do you know where basin forms?
Tanks again for the help
Plate Carree does have the advantage that you can easily run it through a program like G.Projector to get it into a wide range of projections easily. Software that can start in other projections tends to a be a lot more complicated, so you might want to try just drawing the distortion into the map and then projecting it. The distortion takes the form of stretching things out from east to west, with the amount of stretching increasing as you get closer to the poles.
On Earth, The Atlantic is a comparatively "recent" example of an ocean basin forming when North and South America split apart from Africa and Eurasia. The Great Rift Valley, Red Sea, and Gulf of Aden are examples of the same process at much earlier stages.
Thanks again for the help Hai, you're a really good guy
One more thing, can you tell where a lake forms? Is it only where multiple rivers join or it is about the topography of the land?
There are a few lakes that are "Endorheic". The Dead Sea, Aral Sea, Caspian Sea, and Great Salt Lake are all examples. These have no river outlet. Water flows in, and then evaporates. They only occur in quite dry conditions, usually well inland. There are also a few rivers that just spread out over a flood plain and evaporate without flowing into a lake or ocean.