Hello,
Previously when I used this kit, it was to strong for its application.
I heard it was probably the input signal being to strong.
My question: when I chanche the value of R1 to a lower value to allow more bleed to ground, will this work? or am I thinking completely wrong? 
thanks in advance!
link to manual with schematic: https://www.velleman.eu/downloads/0/illustrated/illustrated_assembly_manual_k1803_rev2.pdf
R1 determines the input impedance and has the same value as R4 with the intention of setting the non-inverting input of the op-amp to the obligatory zero voltage.
IC1 acts as an inverting amplifier and the gain here is largely determined by R5/R2. If it is certain that the input signal is too high (just double check anyway: use your mV meter in AC mode and make sure the input signal is 1 kHz) , you can possibly increase R2 or decrease R5.
There are other things you can do :
- Replace the opamp with an NE5532, TL072 which can handle a little more than the LM
- Increase the supply voltage which also improves the headroom of the amplifier.
- Experiment with replacing R2 and R5 with adjustment potentiometers to determine which are the ideal resistance ratios: lots of fun guaranteed.