Can a speed-experienced user explain this to me? : TheGoodSpeedGuide | Torhoo darknet markets

can someone explain me some things about amphetamine.

the situation is as follows,
a good friend of mine asked last year to buy some amphetamine via the darkweb. he had read that this would mean better quality.
so i bought 2 samples on the dark web at the end of last year from good vendors. ( we are from germany )

my friend has no medical or psychological problems and uses amphetamine 3 times a year without any problems at first sight.
never had stimulant psychosis.

The amphetamine was tested for 19% amphetamine, 66% caffeine and DPIA.
we also wash the amphetamine 3 times with dry acetone. we noticed that the acetone turned into a milky foam.
reagent tests where good tbh.

after washing with acetone 1 of the 2 samples smelled like burnt. maybe a bad interaction between chemicals? both samples were white and burnt in nose he said ( caffeine?)
i think the dosage was 0.600mg in 12hours , he did say he had to do 100-150mg lines to feel the rush

when using this amphetamine my friend complained a lot of the following symptoms:
- urge to use more ( like with cocaine he felt like he wanted to keep taking more )
- a tick cough
- fever
- never achieve the desired effect
- voices in his head after 8-10hours amphetamine use
- zero euphoria
- always going through the same loops ( washing hands , tics , being quiet , repeating , coughing )
-3 days of not being able to sleep after a few doses

after use he complained about extreme fatigue for a few days and voices in his head.
and he became increasingly ill after using it for days.
after 1 week everything was back to normal and he functioned as before.

he also always complained that the amphetamine felt very dirty. as if something went wrong with production or something
we repeated this 3 times and always came to the same negative effects from this speed.

his conclusion was actually that he thinks he had used contaminated amphetamine of poor quality.
is this true ?

my question is can amphetamine be contaminated with wrong raw materials that can negate the effect of amphetamine high?
or was caffeine giving him those bad reactions?

i am not talking about cutting but really about contaminated raw materials.