How to update one value in my userData using Laravel

I am trying to update specific value in my user data.

User data can look like this :

User : {
    role : [0, 1],
    name : "x",
    CommonId : 'xxx',
    skills : [
        {
            id : 1,
            name : 'x',
            level : 'null'
        },
        {
            id : 2,
            name : 'x',
            level : 'good
        },
        .........
    ]

First, I have to access the specific user who want to make an update ($user) => (working)

Then, i need to access the skills data and found the one to update ($matchedSkill) => (working)

public function UpdateLevelSkill(Request $request)
{
    $level = $request->get('level');
    $commonId = $request->get('commonId');
    $userId =  $request->get('userId');

    $user = User::where('microsoftId', $userId)->first();
    $skills = $user->skills;

    $matchedSkill = (object) [];

    foreach ($skills as $skill) {
        if ($skill['CommonId'] === $commonId) {
            $matchedSkill = $skill;
            break;
        }
    };

    return response()->json($matchedSkill);
}

When I return matchedSkill, I got the object skills I want to update.
But then, if I add

$matchedSkill->Level = $level;
$user->save();

I got error:
> Attempt to read property "Level" on array"

even if matchedSkill is an array.

How can I update the skill ?

I have tried to use ['Level'] with no success

I have also tried to add condition (if matchedSkill ...)

Updating with consideration that matchedSkill is an array (working):

public function UpdateLevelSkill(Request $request)
{
    $level = $request->get('level');
    $commonId = $request->get('commonId');
    $userId =  $request->get('userId');

    $user = User::where('microsoftId', $userId)->first();
    $skills = $user->skills;

    $matchedSkillIndex = null;

    foreach ($skills as $index => $skill) {
        if ($skill['CommonId'] === $commonId) {
            $matchedSkillIndex = $index;
            break;
        }
    }

    if ($matchedSkillIndex !== null) {
        $matchedSkill = $skills[$matchedSkillIndex];
        $matchedSkill['Level'] = $level;
        $skills[$matchedSkillIndex] = $matchedSkill;
        
        $user->skills = $skills;
        $user->save();

        return response()->json($matchedSkill);
    }

    return response()->json('Skill not found.');
}