Getting back to the main topic:

Q1) Is it improtant to have bosses in levels

Not so much "bosses" as it should be some kind of climax. A boss is where the story, and gameplay change radically, that makes it unique and more exciting from the rest of the game. So it could be some floating monster you have to get into the head of, or a huge space station is exploding and you have three minutes to get out, Its the intended memorable moment in the game that makes it all the more fun.

Q2) Number the following with 1 being most important. What is the most important thing about a mod: Storyline, Gameplay, Desgin of the levels, Weapons, Textures.

Really, I think the most important is environment. A game that does not have a unique or believable environment can't support the story; this is different from a book, or movie. In a game, the player has to not only interact with the story elements, but also the environment elements: those things that arn't there so much as to support the story, but to make the story (and therefore the environment) that much more believable regardless what it is about. Remember, its all about suspension of disbelief. Once you have that nailed, then other elements such as storyline, gameplay, design, weapons, and textures can complement that. Btw, those are my choices in order (respectively).

Q3) What do you think is a good length for a proper half-life 1/2 like mod.

For an amateure user created mod that might strike my attention, I say about 1-3 hours.

Q4) Do you still play half-life1 multiplayer, if yes, how often, and do you play online.

Yes, every now and then, but not very often at all; once every other month I might say. Is there any other way to play Half-Life multiplayer than online?

Q5) Do you own a copy of half-life1

Yes.

Q6) Do you own a copy of half-life2

Yes.

Q7) What difficulty did you choose when you first played half-life1

Normal.

Q8) What difficultys have you finished half-life1 on

Normal.

Q9) If you downloaded reddawn, what difficulty would you play singleplayer on.

Even though I don't know anything about it, still: normal.

Q10) Do you use cheats to finish the half-life 1 campaign. Be honest.

I had to: getting into those sticky clips ruined it for me when I had to reload from my progress on the level before, but noclip is where I drew the line.

Q11) Whats better, a simple storyline or a complex cool story line.

I'll take both if offered. However, a simple storyline would need to be complemented by some new innovative gameplay or leveldesign technique (or I would be looking forward to it). Either that or interesting weapons, or some other interesting idea.

Q12) Do you still check out half-life1 maps and mods and download them or are you more of a half-life2 man.

I'm pretty much a Half-Life 2 man, but if I find those small mods available, or the latest maps in Half-Life 1, I'll give them a look-see (preferably singleplayer).

These are all things that should be decided well before the project is being "finalised"... and if you are still deciding things like this, it helps to have plenty of input from more experienced people as to what works and what doesnt.