Problem with Tiles and Mobs

[Piethon]

Hello.

I am programming a tile based game with pygame.
I am loading different objects, like trees, walls, houses etc. on the surface.
For that, I am using different files.
In the first file, I have my images defined:

WALL_IMG = 'stone_wall2.png'
TREE_IMG = 'tree.png'
HOUSE_IMG = 'houseSmallAlt1.png'
WATER_IMG = 'water.png'

In the second, I am loading them and loading them onto the map:

class Game:
    def __init__(self):
        pg.init()
        self.screen = pg.display.set_mode((WIDTH, HEIGHT))
        pg.display.set_caption(TITLE)
        self.clock = pg.time.Clock()
        self.load_data()

    def load_data(self):
        #Folders
        game_folder = path.dirname(__file__)
        img_folder = path.join(game_folder, 'img')
        mob_folder = path.join(game_folder, 'mobimg')
        player_folder = path.join(game_folder, 'playerimg')
        tile_folder = path.join(game_folder, 'tileimg')

        # Map
        self.map = Map(path.join(game_folder, 'map.txt'))
        #Player IMG
        self.player_img = pg.image.load(path.join(player_folder, PLAYER_IMG)).convert_alpha()
        # Zombie IMGs
        self.zombie_img = pg.image.load(path.join(mob_folder, ZOMBIE_IMG)).convert_alpha()
        # TILE IMG
        self.wall_img = pg.image.load(path.join(tile_folder, WALL_IMG)).convert_alpha()
        self.wall_img = pg.transform.scale(self.wall_img, (TILESIZE, TILESIZE))
        self.tree_img = pg.image.load(path.join(tile_folder, TREE_IMG))
        self.tree_img = pg.transform.scale(self.tree_img, (TILESIZE, TILESIZE))

    def new(self):
        # initialize all variables and do all the setup for a new game
        self.all_sprites = pg.sprite.Group()
        self.walls = pg.sprite.Group()
        self.trees = pg.sprite.Group()
        self.zombies = pg.sprite.Group()
        self.flubbers = pg.sprite.Group()
        self.water = pg.sprite.Group()
        self.blowpipes = pg.sprite.Group()
        for row, tiles in enumerate(self.map.data):
            for col, tile in enumerate(tiles):
                if tile == '1':
                    Wall(self, col, row)
                if tile == '2':
                    Water(self, col, row)
                if tile == '3':
                    Tree(self, col, row)
                if tile == '4':
                    House(self, col, row)
                if tile == 'Z':
                    Zombie(self, col, row)
                if tile == 'P':
                    self.player = Player(self, col, row)
                self.camera = Camera(self.map.width, self.map.height)

    def update(self):
        # update portion of the game loop
        self.all_sprites.update()
        self.camera.update(self.player)
        # And here follows stuff, you don't need to solve the problem

That above is just a part of the whole code. And there is also another file, called tile map. My problem is explained below.

class Map:
    def __init__(self, filename):
        self.data = []
        with open(filename, 'rt') as f:
            for line in f:
                self.data.append(line.strip())

        self.tilewidth = len(self.data[0])
        self.tileheight = len(self.data)
        self.width = self.tilewidth * TILESIZE
        self.height = self.tileheight * TILESIZE

class Camera:
    def __init__(self, width, height):
        self.camera = pg.Rect(0, 0, width, height)
        self.width = width
        self.height = height

    def apply(self, entity):
        return entity.rect.move(self.camera.topleft)

    def update(self, target):
        x = -target.rect.centerx + int(WIDTH / 2)
        y = -target.rect.centery + int(HEIGHT / 2)

        # limit scrolling to map size
        x = min(0, x)  # left
        y = min(0, y)  # top
        x = max(-(self.width - WIDTH), x)  # right
        y = max(-(self.height - HEIGHT), y)  # bottom
        self.camera = pg.Rect(x, y, self.width, self.height)

NOW MY PROBLEM:
I can move my player around the screen (not shown in the code above). And if I walk through trees, that are above my y spawning position, I am on top of them, but if there are trees below that y position I spawned at, I am under them. This is pretty annoying, e.g. I am not seeing myself when I am in water, that is below my y position I spawned at. Because I don't wanna spawn at the edge of the map.
Do you have any idea, how I could fix this problem? I have the same problem with mobs.
I just want to be able to tell python, if I am supposed to be below or upon the object.
Thank you so much for your help (sorry for posting so much code, was necessary).

Piethon