English:
Hey! So I've heard you want to free your old Playstation (or XBOX) memories of San Andreas from all the dust that they have collected over the years of you playing the PC version with all the modifications that you are used to. Now, after 10 years I think it's time to get all the features that, in the first place, should have been featured in all versions of GTA San Andreas. Every version has it's advantages and disadvantages. So let's only focus on the advantages of each version and add these to the "modificationable" PC version. Since many modders including format c:, The Hero and Silent brought back features known from other versions of San Andreas in form of plugins, I thought that it is now my turn to try to bring back a feature that I missed the most of them all:
The two player missions.

The first time that I played San Andreas it was at a friend's house on a Playstation 2 (the big one). We played the whole night through only in two player mode! I still remember that my friend had all savegame slots occupied. It was always a finished savegame but saved at different places! One in Los Santos, one at the abandoned airstrip and so on. One thing I can tell you is that I was hooked. In Verdant Meadows the screen was all orange and red and you thought you were actually in Death Valley. Still the best part of the game was playing together, in my opinion. Friend loading the savegame and showing me the achivements and what has been done in the game while in two player mode. Now many of you certainly tried the same thing on PC and some may also expected the PC version to feature all of this but then realized that it is all gone on PC and what you get is a pared-down version of the beauty that was the first edition.
(Even the 'remastered' version of San Andreas for Xbox 360/iOS/Android/PC doesn't include the 16 coop missions!)

Now, with this modification you can refresh your memories and show your friends what
you have achieved and play the (now additional) 16 missions you already had on the
Playstation 2 and XBOX. Just install CLEO, drag and drop this mod into the CLEO folder, get a program to control the second player and load up your old savegame that you are used to with all your achievements, gang territories and clothes.

If you don't like a certain feature you are able to change essential features in the
Two Player Missions Options.ini file I provided.

Deutsch:
Mit diesem Cleoskript bekommt ihr die Co-op missionen aus der PS2 und Xbox version von San Andreas. Ihr braucht dabei keine main.scm ersetzen. Das bedeutet ihr braucht kein neues Spiel zu starten! Weitere Vorteile gegenüber den anderen 2 Spieler-mods sind die ganzen Optionen, die euch zur Verfügung stehen. Einfach die Two Player Missions Options.ini im Two Player Missions-Ordner öffnen und beliebig personalisieren. So können beispielsweise zwei Fahrzeuge gleichzeitig gefahren werden, was auf der PS2 und Xbox nicht möglich war.

Um den zweiten Spieler zu kontrollieren empfiehlt es sich mindestens ein Gamepad zu besitzen. Ladet euch dann Ginput von SilentPL herunter und installiert es.
http://www.gtagarage.com/mods/show.php?id=24272
Falls wirklich nur ein Gamepad vorhanden ist, muss in den Optionen von Ginput (GinputSA.ini) MapPadOneToPadTwo=1 gesetzt werden. Dann spielt der erste Spieler CJ mit der Tastatur ganz normal und der zweite Spieler sucht sich einen Skin aus und spielt mit dem Gamepad. Falls ihr kein Xbox 360 Gamepad besitzt muss zusätzlich noch ein Xinput-wrapper verwendet werden. Den besten erhaltet ihr hier:
https://github.com/x360ce/x360ce