The line keeps welding together wont advance from

Usually you unscrew the end knob anticlockwise to remove the line carrier,or spool

To advance the line on a trimmer just push down in the center of the spool head then pull on both lines at the same time and it should release and inch or so of line. If it has a spring on the inside of the head then just tap it in the center of the head on a hard corner surface while its running and it will release more line out. That is what ya call a bump feeder as such.

Pull the head off by turning the inner hub counter clockwise while holding the outer head still. Once the inner head pops out, turn it over and look for the string rotation arrow. If you can't find the string winding directional arrow, start the trimmer and determine shaft rotation direction (generally counter clockwise) and wind the string in the same direction as the head rotates when installed.
Pull about 5 arm lengths of string out of a string spool and cut it off. Place the inner trimmer head on an object that will hold it while you pull the string to even lengths through the winding hole (the support brackets of a pickup truck tail gate work well for holding the inner head while doing this).
Begin wrapping the string double wraps in the proper direction, laying them evenly and closely to the previous wrap, working it back and forth as the string begins to build up. Avoid crossing the string over itself more than necessary, the string can weld itself together if the strands cross to awkwardly. Once the string is wound, hold the head with one hand and slide the string through the outer head holes, avoid letting the string come unwrapped.
Carefully place the inner head down into the outer header. Avoid letting the string get caught between the inner and outer head. Once the heads are together lock the inner head onto the outer head by turning it and locking the round knobs into the outer head slots.
You can trim the string or let the trimmer guard do it. If the string doesn't feed it is either wound the wrong way, tangled between the inner/outer head or welded to itself.

pull the head completely off and make sure that the shaft is not broken, if not then line it back into the head slot and put back together and test it out, Tim

These little electric machines have an automatic line feeding system. Do not bump the trimmer head on the ground attempting to make line advance. If the line advance is not functioning like it should, then the string head should be removed and the spool inspected for snags and tangles.

string wont come out? or head not turning?

this is usually an indication that the line you're using is too small in diameter. try the next larger size line.

I would take off the head and have the spring replaced that keeps the button down when using.