Hi GuiPotia,
Ideally when using a lot of static meshes, like the ones you’ve painted with the foliage tool, it wouldn’t be ideal to use static lighting. You currently have ~42k assets painted with the foliage tool. To build lighting for this amount of assets would take a long time, use a large amount of RAM in the process, and storing the lightmap textures for these assets would likely give more issue than using only dynamic lighting.
Since you do mention that you’re using a day/night system you shouldn’t have the need to build lighting for anything in your scene since the movable light will negate the use of any static lighting. If you intend for your project to not use static lighting at all I would suggest going into the Project Setting > Rendering category and then disable the option for “Allow Static Lighting”, however, if you intend to use static lighting in some additional levels, but just not this one, then you can go to the World Settings and enable “Force No Precomputed Lighting”. This option will disable static lighting for this specific level and not for the entire project.
Generally speaking though, larger open worlds with a lot of dense foliage are not ideal for static lighting. Typically you wouldn’t want to use static lighting on objects that would need to move anyhow, like with trees or grass swaying to wind. The statically baked shadow will not move and break any sense of realism you may want for your scene.
I hope this helps.
Tim