Yii2 multilingual slug and language switcher that will "respect" translated slug's

Question

The problem is - I can't figure out how to switch to translated slug:

I've implemented multilingual slugs using lav45/yii2-translated-behavior.

Database is quite simple:

Portfolio model:

id | created_at | is_active

PortfolioLang model:

portfolio_id | lang_id | title | content

So far - so good. I have a actionView that calls out translated content as follows:

    protected function findModelBySlug($slug)
    {
        if (($model = Portfolio::findOne(['slug' => $slug])) !== null) {
            return $model;
        } else {
            throw new NotFoundHttpException();
        }
    }

    public function actionView($_lang, $slug)
    {
        $portfolioLang = PortfolioLang::findOne(['lang_id' => $_lang,'slug' => $slug]);

        $model = $portfolioLang->portfolio;
        
        $pictures = PortfolioPicture::find()->where(['portfolio_id' => $model->id])->orderBy(['sorting'=>SORT_ASC])->all();       

        return $this->render('view', [
            'model' => $model,
            'picture' => $pictures,
            'langList' => Lang::getList(),
        ]);
    }

Must note, that this is working, "until" it try to switch between languages while I'm opened the entry.

I was using example code from here: https://github.com/lav45/yii2-translated-behavior-demo/blob/master/frontend/components/LangHelper.php

I guess that I need something else than a sample code (it looks like it works only for current ID's for existing entries). Could you, someone, give me some hints for the next step?

Thanks in advance!