make a fresh install of the game / delete efconfig.cfg from the /BaseEf directory.

launch the game once and make all your settings, but do not make any changes to resolution. the game will crash when you set resolutions higher than 1152x854 but you can specifiy higher custom resolutions in the config file.

you can set any graphic option you want just leave resolution untouched.

after youve finished configuration close the game and open efconfig.cfg in the /BaseEF directory.

find and adapt the following settings to your need:

seta r_customaspect "1"
seta r_customheight "1080"
seta r_customwidth "1920"
seta r_fullscreen "0"
seta r_mode "-1"

now the game will launch in windowed mode and you can swap between fullscreen and windowed mode with ALT+ENTER.

while the game is reloading after youve pressed ALT+ENTER you can ALT+TAB out of the game onto desktop but this only works while the game is reloading and while you are not in main menu because the loading times will be too fast to switch out.

you can swap easier while inside a level or when you are in windowed mode already and are using the console you are free to ALT+TAB back and forth and the mouse is not constrained to the game window anymore.

once you are in windowed mode and bring up the console the mouse can leave the game window. there is no borderless windowed fullscreen mode. you can only switch between windowed mode and exclusive fullscreen.

keep r_smp to 0 or the game will freeze on certain levels.

if you need vertical sync be sure to add the following commands to the config because the game fails to activate vsync by itself from the menu.

(change display refresh and max fps to your monitors respective refresh rate; 75, 120, 144, etc.):
seta r_swapinterval "1" (1= vsync on, 0=vsync off)^
seta r_finish "1"
seta r_displayrefresh "60" (refresh rate from your monitor)
seta com_maxfps "60" (fps limit)

further tweaks:

seta com_hunkmegs "512" or "1024" (default 36)
seta com_zoneMegs "2048"
seta lod_bias "-2" or "0" (default)
seta r_finish "0" or "1"
seta cg_marks "1"
seta cg_shadows "1" or "2" (default 3)
seta r_roundImagesDown "-1" (i believe this fixed texture corruption from the phaser)
seta r_detailtextures "1"
seta r_texturebits "32"
seta r_colorbits "32"
seta r_stencilbits "8"
seta r_depthbits "32"
seta r_overBrightBits "0"
seta r_ignorehwgamma "0"
seta r_subdivisions "1"
seta r_lodCurveError "10000"
seta r_flares "1"
seta r_dynamiclight "1"
seta r_picmip "-1"
seta r_picmipmin "-1"
seta r_dynamiclight "1"
seta r_vertexlight "0"

when making changes from the console ^ type vid_restart to restart the engine and apply your settings.

https://www.gamesurge.com/pc/hardware/tweaks/q3atweak.shtml

Thank you :)
It fixed the Hunk_AllocateTempMemory error :)