I have some questions
1. How to add new weapons to game?
2. How to change weapon using script?
3. Why waypoint mode dont work?
4. When will be ready standalone multiplayer?

1. How to add new weapons to game?

Its not for the faint hearted and if your starting from creation to the final result it could take you a good 18 months or more
Your better off asking in the "3rd Party Models and Media" section or start with lots of You Tube tutorials..

2. How to change weapon using script?

Asking in the Script section would be better for this ....you would need to explain what you want to achieve...

3. Why waypoint mode dont work?

Waypoints work fine for me ..... Can you be more specific of your problem and I may be able to help..

4. When will be ready standalone multiplayer?

That's will be implemented when voted in by the community .... Its on the voting list here under Multiplayer
https://www.game-guru.com/feature-vote

Cast your vote using the slider ... All the way up to use your full vote ..

Lucky you.

For me, sometimes they work, sometimes they don't, and I have no idea why, ?
This is something that goes way back to the early versions of FPSCR, and it is still
the same today in GG, but I guess Lee will sort it out eventually, along with everything
else.

1. I want to add like 15 weapons with same model but different effects.
2. Can u answer me?
3. When i choose waypoint mode and press on map nothing changing.

@SneakBug8

The answers you are looking for regarding your weapons reside in the threads I suggested ....
I'm afraid I am no gun modeller, Rigger or scripter ... and you need the knowledge of all.

When you create a waypoint please make sure you are in Top/Down View first ... By pressing "G"
Then try placing your waypoints .....

you need to click the "add new waypoint" button, then a small coloured dot will appear on the screen (you may need to zoom down a bit if you can't see it), then you can shift-click this dot to create new 'linked' dots which act as the path when dragged away from the other dot(s)

for the weapon once you have 1 set up and working you can simply copy and paste the folders and rename them to make 15 versions but changing the required "effects" or whatever each time.

it's likely you can can copy and paste the standard weapon that is closest to the one you are after and then adjust the models as you wish (gamecore\guns & entitybank\*folder*)

to change weapon via script is either
AddPlayerWeapon(e)
or
ReplacePlayerWeapon(e)

the 'e' refers to the entity number of the gun to give and the replace command simply replaces the currently held weapon (that's as specific as the commands get... there's still a lot of work needed as far as weapons go)