if/else doese not work in my POST Method of SpringBoot rest api

I use Spring Boot rest api with MongoDB. In the POST Method, if there is not scoreID and there is not a player with specific date in my collection, because at the same time a player cannot play different games and bring score, then if the specific player and gamecode exist, create a score. In fact, in the POST Method I used Nested IF-ELSE conditions. But, in the Postman when I execute POST Request with this data: { "scoreid":"s11", "score":1000, "player":"sahari", "gamecode":"g12", "date":"2020-01-01" }

always, I recieve an error, in the Postman, 400 Bad Request!, which i defined in the last line of my IF-ELSE statements. I do not know, what is my mistake and why my program doese not execute IF conditions correct.

The POST Method:

//Create Score
    @PostMapping
    public ResponseEntity<?> createScore(@RequestBody @JsonView(Views.class) @Valid  Score score) {

        String p = srepo.findByPlayerName(score.getPlayer());
        String g = srepo.findByGameCode(score.getGamecode());
        String scoreid = srepo.findByScoreid(score.getScoreid());
        Query query = new Query();
        query.addCriteria(new Criteria().andOperator(Criteria.where("player").is(score.getPlayer()),
                Criteria.where("date").is(score.getDate())));
        if((scoreid != null)) {
            return ResponseEntity.status(409).body("Conflict!");            }
        else 
            if(mongoTemplate.exists(query, Score.class))
                return ResponseEntity.status(409).body("There is not Possible at same time one player brings different Scores!");
            else
                if((p!= null)&&(g!= null))
                {
                    history = new ArrayList<History>();
                    h = new History();
                    h.setScore(score.getScore());
                    h.setDate(score.getDate());
                    history.add(h);
                    hrepo.save(h);
                    score.setHistory(history);
                    srepo.insert(score);
                    return ResponseEntity.ok(score);
                    }
                else
                {
                    return ResponseEntity.status(400).body("Bad Request!");
                }


    }

The Score Repository:

 @Repository
public interface ScoreRepository extends MongoRepository<Score, String>{


    @Query("{'scoreid':?0}")
    public String findByScoreid(String scoreid);

    @Query("{'Player.nickname':?0}")
    public String findByPlayerName(String player);

    @Query("{'Games.code':?0}")
    public String findByGameCode(String game);
}