Solution is already in the MX PDF help file page number 220.

Anyway someone kind person (gandjcarr) forwarded this question to me.

First of all open Pdf help of your Music Maker MX go to page number 220. Here is a copied text

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Adapt waves automatically to the BPM: When loading to the arrangement or
previewing, MAGIX Music Maker MX tries to adapt the samples to the speed of
the arrangement. This always works properly with newer MAGIX soundpool
samples as the tempo information is saved in the wave file. It usually works
with all other loops as well, provided the loops are clean, that is, they are cut
to entire bar lengths (see the Arranger chapter).
With "For patched samples only", automatic timestretching can be deactivated
for all other samples. With "Apply to longer samples as well", longer samples
will also be adapted if they contain tempo and bar information provided by the
Remix Agent.
Remix Agent for the tempo and beat recognition of longer samples (>15 s):
Here you can deactivate the automatic opening of the Remix Agent for longer
samples (for example, CD tracks or MP3s).
Automatically adjust waves to pitch: A wave's pitch can be adjusted
automatically using pitchshifting. For this to work however, the used samples
(much like the samples on the MAGIX soundpool CDs) must have the
corresponding key and pitch information. The pitch of the arrangement will
then correspond to the pitch information of the first sample in the arrangement.
Use destructive adjustment for shorter samples: Usually, loaded samples are
adapted to the arrangement in realtime with timestretching. For computers
with lower processing power, this method can be deactivated – the
timestretching effect will then be calculated into a new file which is copied to
the hard disk.

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You have to read and select which part you want to apply from the above text.

To open Program settings window for deactivation

"Program settings",click on  Import" tab look at your left side. There are various check boxes check and uncheck as you wish. You can also open Program settings (Y key or "File" menu > "Settings" > "Program settings").

For help here is a screen shot where you can deactivate auto BPM as you are asking. This screen shot is from MMM 16 Premium, in your Music Maker MX click  "Y" key. Please look at red marked items.

I hope now your problem will be solved.

Extra:Page 89 Pdf help Music Maker MX
Loop Finder
The Loop Finder has been developed to find the BPM in short rhythmic
passages, to integrate short loops in an existing arrangement, or to yield drum
loops from short rhythmic passages. Otherwise, the BPM Finder helps in this
regard.