Is 1400 a good rating for a chess player after 6 months?

Well I've been playing for 45 years and I can't break 1300 in blitz here so I'd say your improvement is phenomenal. 

If only that were true ... I'd  have a GM stamp next to my name 

Bad habits can be difficult. I've played chess even longer. As most of this chess has been against weak players, I have many self-destructive habits that have been rewarded instead of punished.

If you want to play well, you must play against players who understand the game.

There are far too many other factors at play to determine that.  For example, say both players are playing daily games, but player A is making heavy use of the opening book while player B never uses it.  This means player A almost never makes a mistake in the opening, but also does not learn from the mistakes he would have made.  Thus, when he sits down at the board and does not have an opening database to consult, he is on his own from move 1.

I have a couple friends from a local club who are much higher rated than me (2000+) OTB, yet have lower online ratings that me.  Some of that is due to how they use online (for experimentation), but it also has to do with simply playing more games online.  Online ratings mean exactly nothing, and there is no way to consistently correlate online ratings to OTB ratings.

With that said, if you see someone with a sub-1200 online rating, you can be fairly certain (assuming they have enough games under their belt) that they are not a Class C or higher player, but you cannot assume that someone with a 2000 online rating is an expert, or even a Class A player (assuming no nefarious actions from them, that is).

That does not change anything.  There are players who are 1800+ in the chess.com blitz ratings who would not (and some, in fact, are not) rated higher than 1000 in OTB blitz.  A simple example to show this:  2 friends join the site and select 1200 as their starting rating.  They then play a match where player A wins 16 of 20 games and ends up with a 1600+ rating, while the other ends up around 900.  In reality, both players are sub-1100 players with player A being stronger (say, 1000 vs 600 for player B).  Yes, you can tell that player A is stronger than player B, in this case, because they have played each other.  Introduce player C who is rated 1500 after playing several opponents of varying strengths with mixed results.  Who is stronger:  Player A with the 1600+ rating, or Player C with the 1500 rating?  (The answer:  there is no way to tell!)

That does not change anything.  There are players who are 1800+ in the chess.com blitz ratings who would not (and some, in fact, are not) rated higher than 1000 in OTB blitz.  A simple example to show this:  2 friends join the site and select 1200 as their starting rating.  They then play a match where player A wins 16 of 20 games and ends up with a 1600+ rating, while the other ends up around 900.  In reality, both players are sub-1100 players with player A being stronger (say, 1000 vs 600 for player B).  Yes, you can tell that player A is stronger than player B, in this case, because they have played each other.  Introduce player C who is rated 1500 after playing several opponents of varying strengths with mixed results.  Who is stronger:  Player A with the 1600+ rating, or Player C with the 1500 rating?  (The answer:  there is no way to tell!)

Even in your small sample size,

Not that small actually

you notice there is a gap between all of the ratings (and some fairly large differences in several of them).

That's the whole point of looking at the data, to see how they compare

 Don't get too hung up on your rating, or you may not be willing to experiment with new openings, lines, etc.

Hello everybody,

I've begun chess 6 months ago and I wanted to know your personal experiment and how long does it take to become a 2000 rated player if we are determined?

thanks for your answers

no way OP learned the moves 6 months ago and is now 2000+ at blitz..NO WAY...! obvious engine cheater

 I don't think so. At the chess site I rated 2264 and otb rating 2011 uscf, I told a player my rating 2264, they will assume fide or uscf, not online. The only rating respect otb rating not online rating. I know fplayers who atre rated 2500 to 2600 online, I sorry but they don't count. No online player who has a high rating is GM without having the title from FIDE.