I suggest you get a paediatric audiology (hearing) assessment done at one of the hospitals before approaching a speech therapist if you haven't already done so. It is much more detailed and specialised than the hearing test the GP does. We used the American Hospital 7 years ago for both hearing and speech assessment; unfortunately they didn't pick up my son's hearing problem, so I can't honestly recommend them for that, but they correctly assessed his speech delay and the hearing problem was picked up in the UK later. He had speech therapy at Rashid Paediatric Centre near MOE and they did a great job with him. Good luck with finding the help you need.
In particular, sounds s, c and z. I would like to see someone and get some exercises to correct it. I am guessing that we need to see a speech therapist? Anyone has any good recommendations? Thank you