The camera lense comes out but does not automatically returns

How new? Can you still return it?

Chech wether something is not stuck between yopur lenses of camera.....it is dfue to...that something is stoping the lenses to come out...there might be something betwwen lense and camera walls...check it out..

There's nothing you can do yourself to fix it, the lens should focus down to 0.4m (15").

The lens comes with an automatic one year manufacturer's warranty, which extends by another three years if you registered the warranty so I suggest that you return the lens to Sigma for repair.

Note that any evidence of misuse or unauthorised repair attempts automatically invalidate the warranty.

You don't state which Takumar model you have, but your camera is behaving entirely correctly.

The built in flash on the SF10 is automatically disabled when certain lenses are used, this is because the low position and narrow coverage of the flash combined with the size of many lenses causes the light path of the flash to be blocked or the flash coverage will simply be too narrow for some wide angle lenses; this can create vignetting or other dark shadows from the lens to appear in the photo. When a proper SMC-Pentax F lens is used the camera will warn you of this, but third party lenses like the Takumar lack the ability to trigger the warnings.

Built in flash units on all SLR's are just a handy get-you-by feature for parties and snapshots using standard lenses. For all other use, there simply is no substitute for using a proper external flash.

I suggest that you read the manual, if you don't have it then you can download it for free from here.

I trust that my answer has fully resolved your question; if so then please return the favour by rating my answer.

Look in the menu, there's an option to switch between 1 minute and 0 seconds (=never) switch off.

Use the vacuum cleaner to suckout the dust/sand particles stuck between the lens casing and the body.

F-- means that the camera cannot find an apeture with the other settings that it is on put yur ISO on auto and put the camera in automatic mode and it should work but it might be a problem with the apeture in the lense, in which case it would be very hard to fix and you would probably end up desroying the lense in the process, if you did not go to a specialist.

I had the same problem (same kit). I even exchanged the kit for a new one, and had the same issue. I'm convinced it's the connection between the camera and the lense - when I wiggled the lense, it would sometimes return to normal. I considered cleaning the contact points, but then the problem went away. I've been shooting hundreds of times, without it happening once.

thats normal.
it just doesn't have enough power to bring the lense back in.
once you charge your battery and turn it on the lense will automatically come back in and then out for you to take a picture.

Make sure the lense is not bent. If so, gently straighten it. This worked with mine.