Embedded C programming Loop pedal

General information for the business: Creating consumers electronics
Kind of development: New program from scratch
Description of requirements/functionality: I need somebody to write C code for an embedded chip to create a music loop pedal. It must be able to
- Record sound from a microphone
- Store the sound on a serial flash chip
- Be able to play the sound back through a DAC
- Play multiple tracks back simultaneously
- Record at the same time as music playback
- Take interrupts to record, stop, start,
- Take interrupt to remove the last recorded track

The functionality should be as follows,
- Press and hold record
- Make sound
- Stop holding record
- Recording should be played back in a loop
- User can then press and hold record again whilst first track is still playing -
- Record sound
- Stop holding record
- Now both tracks will be playing at the same time
- If the remove track button is pressed, the last recorded track will be removed but the rest will keep playing
- If the pause button is pressed all sound will stop, then when play is pressed again all tracks will play
- There will be a restart button which removes all tracks

The code will be for the breakout board STM32F411E an ARM® Cortex®-M4 based chip.
Serial flash chip example - W25Q64JVSSIQ
Example similar functionality - https://m.youtube.com/watch?v=48bk_vdY2Gg
Specific technologies required: C
Extra notes: I have some initial code which can playback sound, but it is not well written.
I have been using CoIde to get this working so far.
I know programming so might be able to help with some issues.