abdulraheem123, I dont think its a requirement that you must have your birth certificates but as I had mine and she had hers we just included it (the more docs you can provide the better, thats the way I see it). If you dont have something then either dont mention it or if its something important try explain why you dont have it, Im sure they will understand.
sponsorship undertaking form:
https://www.gov.uk/government/uploads/s ... p-form.pdf
yasen, Im fortunate to have had about 37k in savings which I showed and hopefully thats going to help. I didnt actually go to a solicitor for anything other than them to attest my passport, birth certificate, my mums passport and that was it I think. My wife got her docs attested by solicitor in pak though.
You should be fine, as long as you meet the adequate maintenance level which is something like 120 pounds a week I believe, for the next 2.5 years. As long as the ECO can see you have this much projected income either from income sources or savings for next 2.5 years then they cant reject you on financial grounds. best of luck