So can i say that lymph flows from extra cellular space back into the blood?
Yes. The lymph formed from interstitial fluid (accumulated in extracellular space) is collected through the lymph capillaries. It is then transported through lymph vessels to lymph nodes, before emptying ultimately into the right or the left subclavein vein, where it mixes back with blood. Only, the valves prevent the backflow of lymph from blood back into tissue spaces.