I have a tailor professional given to me by friend and the stitch is not holding all of a sudden

Stitching coming out is usually an indication that the top or bottom thread is not under tension during seaming.

Check the bobbin thread is under tension (held by a tension spring) and is firm if you pull gently on it.

Ditto for the top tension, dial should be set to a mid number like 5, lower the pressure foot and then pull the thread just before the needle. Does it feel firm?

If you don't have a manual or aren't sure on threading path, its a good idea to track down a manual on-line or a generic threading diagram may suit.

Try www.sewing.about.com, www.sewingpartsonline.com or www.sewingonline.co.uk to try and find the info specific for your machine.