So anyone wondering, to fix the bug where there is not any collision, you should erase anything written in the content.xml and put this :
<?xml version="1.0" encoding="utf-8"?>
<CDataFileMgr__ContentsOfDataFileXml>
<disabledFiles />
<includedXmlFiles />
<includedDataFiles />
<dataFiles>
<Item>
<filename>dlc_military:/%PLATFORM%/levels/gta5/military.rpf</filename>
<fileType>RPF_FILE</fileType>
<overlay value="false" />
<disabled value="true" />
<persistent value="true" />
</Item>
<Item>
<filename>dlc_military:/%PLATFORM%/levels/gta5/military_metadata.rpf</filename>
<fileType>RPF_FILE</fileType>
<overlay value="false" />
<disabled value="true" />
<persistent value="true" />
<contents>CONTENTS_DLC_MAP_DATA</contents>
</Item>
</dataFiles>
<contentChangeSets>
<Item>
<changeSetName>CCS_military_NG_STREAMING_MAP</changeSetName>
<filesToEnable>
<Item>dlc_military:/%PLATFORM%/levels/gta5/military.rpf</Item>
<Item>dlc_military:/%PLATFORM%/levels/gta5/military_metadata.rpf</Item>
</filesToEnable>
<executionConditions>
<activeChangesetConditions>
</activeChangesetConditions>
<genericConditions>$level=MO_JIM_L11</genericConditions>
</executionConditions>
</Item>
</contentChangeSets>
<patchFiles />
</CDataFileMgr__ContentsOfDataFileXml>

What i replaced there is instead of having

"false"
"false"
"false"
in each paragraphs where its written, i wrote

"false"
"true"
"true"

It brings back collisions, and it works in most of the add ons maps that dont have any colisions at all, i learnt this from the french riviera mod bug whitch was the same bug as this one