Correct & Finalize/Improve EEG Arduino Shield

I need an experienced electronics engineer to review, correct, and finalize an existing EEG Arduino Shield design in KiCad (using Olimex active electrodes). The previous version had design errors that caused component overheating and damaged the Arduino, so I need a full review of the schematic and PCB, correction of safety/design flaws (especially power regulation, input protection, and biasing), proper input/output isolation if necessary, and a finalized, safe, fully functional design ready for fabrication (Gerbers + BOM + assembly files). Please include a clear explanation of the corrections and simulation or theoretical verification proving the design is electrically sound and works 100%. The circuit is almost finished and should not require much work; I’m looking for a senior professional to verify it and help us add any improvements we could implement. The signal output must be safe and within the Arduino ADC range. I will provide the current non-working KiCad project, the original schematic and BOM, photos and a failure description, and the scope of use/environment. Fixed budget: €50.