Sorry to hear that you are havign a rough time. Having been in an AST where I took the agent to the property ombudsman and won my case, try not to stress about it all.
I note your tenancy agreement states that repairs should be reported to the property manager. At the point of signing your tenancy you should have received a copy of how to report any issues (i.e. repairs) and a time frame of how long you should expect to wait for the repairs to be completed (for ex. Urgent (flood, roof leaking=24 hours; medium (i.e. window lock wont lock) = 7 days; non-urgent = maximum of 28 days - get confirmation if this is business or calendar days!). If you haven’t got this then request it immediately and give a 7 calendar day deadline to receive it. Likewise you should have received a copy of their complaint procedure, including escalation and an independant body (1st tier property tribunal, property ombudsman) if the complaint cannot be resolved. Again if you haven’t got this then request a copy with a 7 day deadline.
Ensure everything is documented, and photo’s taken of any repair required. If you have called the property manager on the phone, follow that up in writing (email) enclosing evidence. If the Property Manager fails to complete the repair by the relevant deadline, then escalate, but also lodge an official complaint (note there should be a timeframe for any complaints to be responded to). Detail the complaint clearly (using bullet points) so it is easy for the Property Manager to understand, include any evidence, include a short section of how you want the complaint resolved.
Finally before you escalate to the 1st tier tribunal or property ombudsman you must have given the company sufficient time to resolve your complaint (1 month), including via their escalation procedures (potentially a further month) and received a “final response” letter. If the property manager refuses to converse with you initially and after escalation (ensure you keep proof) after a certain period of days (not sure how long) you could then escalate to the 1st Tier Housing Tribunal. Get confirmation of this from Shelter/CAB before taking that action.
Note you also have the right under the Housing (Scotland) Act 1987 to request the landlord’s contact address. You should request this is writing, hand it to the agent and if they refuse to sign, again follow this up in writing via email. If you want to send it via email, ensure you include a (return receipt), although in Law I’m not certain whether email is classified as delivering the notice. If they refuse to provide this to you within 21 calendar days they are committing a criminal offence. Copy of Legislation here: https://www.legislation.gov.uk/ukpga/1987/26/section/327, and I have attached a draft copy of a letter (via jpeg) within this response.
Pretty sure that covers it. Do not be afraid to challenge, however daunting it may seem, you do not deserve to be treated badly by the agent even if the Landlord treats you fairly.