Samsung's first foldable smartphone will go on sale in September after problems with the device delayed its initial release.The April launch of the Galaxy Fold was postponed after early reviewers reported broken screens.Samsung said it had made "improvements" to the nearly $2,000 (£1,603) device which would be sold in "select markets".The firm has been racing to launch a folding smartphone before its rivals."Samsung has taken the time to fully evaluate the product design, make necessary improvements and run rigorous tests," the company said in a statement.Improvements include extending a protective layer to make it clear it is not meant to be removed, as well as strengthening the hinge area with new protection caps.One explanation for the broken screens appears to have been that some reviewers removed a film which they thought was a typical protective layer that came with the phone when first bought.The defects with the device proved a source of embarrassment for Samsung which has seen declining smartphone sales and faces growing competition from rivals including China's Huawei.Huawei became the second-largest smartphone seller in the world last year and plans to launch its folding smartphone in September.The company also pushed back the release of its foldable phone, saying it wanted to conduct extra tests following the screen problems with Samsung's Galaxy Fold.Earlier this year, Chinese technology firm Xiaomi unveiled a prototype of a folding smartphone that transforms into a tablet.