Ok, this game is probably one of the most open-ended world games out there, but then TOO much exploration leads to possible game-breaking bugs. and I would really like to avoid re-playing from the beginning again....I spent so much valuable hours and my character is already level 20....
I am currently on Chapter 3, where I'm supposed to find a relief for Vatras. I'm unable to continue.....

-I got the 2 ornaments from killing the Stone Sentinels on chapter 2 BEFORE getting quest about Stone circles. Also, after activating the stone circle at Lobart's Farm, "The Portal" Quest suddenly was added into my Journal. (Possibly triggered a quest bug)

-I have looked all around Khorinis, and couldn't find a relief for Vatras.

-Repaired the Eye of Innos with Bennet's Help, BEFORE talking to Vatras about the Eye. (Possibly triggered a quest Bug)

-I finished the 'Ring of water' Quest on Chpter 3 and got the Approval letter and Ring from Vatras.

-I talked to Lares about the Ornament (which I got from Vatras) which he could get me to the Water Mages or something like that, but after choosing all the dialogue options and END conversation, he STILL STOOD there on the Khorinis Harbor. Talked to him again, and still no option of

-"The Missing People" Quest which I never completed even till now, with Patrick's name not being mentioned (cause I didn't do the Cord's quest about Patrick) in the quest description.

-Killed Dexter and his gang of bandits in Chapter 2 just because I explored the his place (No QUEST about killing him or Referring to him that time) .Now, Cord doesn't talk about his lost buddy Patrick. (Possibly triggered ANOTHER Quest bug)...

-One Failed Quest - Brazen Thief. Failed it in Chapter 1.

The reason I included the Missing people quest, cause I think its connected to the whole main storyline...
So there you have it, I totally MESSED up the quest ordering...I know i obviously done something wrong...But is there a way how to continue the game's main quest without ever to start the game all over again? I'll use cheats (if thats possible) as last resort in order to continue the storyline.

Not sure if I can help but I will try :-)

Missing people quest: When you killed Dexter you should have found a letter. When you read it you can go to Vatras to complete the quest. Also this quest is from the Gothic 2 addon, so you don't need it to complete the main story line and even for the addon story line it is not required if I remember correctly.

Relief for Vatras: To complete this quest you need to finish the AddOn story line in Jharkendar, since after that Myxir will be the relief.

For Lares to accompany you to the water mages you need to show the aquamarin ring (by wearing it) to Baltram at the market place.

Hope some of this helps you, if not try to provide a bit more details about what you did, so that I can know better where exactly along the story line you are stuck :-)

Thanks for the Reply.

Missing people quest - I've re-read the letter then tried talking to Vatras again. No new dialogue options shown. I think I've actually completed the quest, I mean there's a new quest I've got about Raven. But somehow, the Missing people quest is still in my current quest....

And I've also talked to Baltram while wearing the aquamarine ring, but his dialogue options are just :
-Show Wares
-END
And when chose the show wares option, he won't sell things to me as I'm a mercenary (I forgot I mention what guild I'm in, Sorry about that.)

I'm have no idea what to do now.

Thanks for replying.

The cheat did work and I had fun. Seeing a naked Lord Hagen running around beating the entire town up is a really amusing scene to watch. My god Hagen, he's f**kin level 60!

Anyways, in the end I just went on myself to the ruins where the water mages are, of course now, without the cheats. Looks like I didnt actually need Lares help to get to the ruins. In other words, I think I can continue my quest from here.

As far as I remember, anytime an offer to lead you there is made, it is not necessary to take them up on it. What it does is show you the way if you don't know and the person leading you there will score points for you if anything is killed along the way, Handy if you are too weak to do it yourself.