Unhappy Samsung Galaxy Camera External wireless microphone

Hello everyone.
I need some help.
I have a Galaxy Camera I use to record press conferences.
Sometimes I can not be near to the speaker and the audio is low.

I have a very limited budget and can not buy an external microphone professional.
I tried to use Btmono and a bluetooth headset, but the camera app only uses the microphone of the machine. If I install a voice recorder, still works perfectly coupled Btmono and bluetooth headset.

I have seen that there are transmitters and receivers bluetooth with 3.5mm attack, but I do not know if it will work; in case I have no idea how I could connect everything.

Do you have suggestions?

Thank you all for any suggestions