I have never heard of Openda before to be honest but his 21 goals for Lens in the Ligue 1 last year are definitely pretty impressive and he was definitely one of the most important reasons why RC Lens was able to finish the last season on position 2 of the french league even before clubs like Lyon, Marseille and Monaco and only 1 point behind PSG.
Regarding Halstenberg: i first heard rumors that he might join Hannover 96 a few weeks ago and now it seems to happen. Halstenberg is a current player for the german national team, with a transfer to a club of the second Bundesliga i think he is risking his spot in the national team for the upcoming EURO 2024 which is played in Germany.