您可以为每个图像使用单独的div，而不是将image用作h2标签的background-imgage，如下所示：

<div id="gallery">
    <div class="image">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>Concert<h2>
    </div>
    <div class="image">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>Concert<h2>
    </div>
    <div class="image">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>Concert<h2>
    </div>
    <div class="image">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>Concert<h2>
    </div>
    <div class="image">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>Concert<h2>
    </div>
</div>

对于CSS，您可以使用flex，如下所示：

#gallery{
    display:flex;
    width: 80%;
    flex-wrap: wrap;
 }
.image{width: 33%}

使用<h2>标签的“background-image”不是正确的方法。您应该创建一个<div>，其中您放置了一个<img>作为图像，一个<h2>作为文本。或者您可以在图像上使用伪元素，而不是<h2>和<div>。如果您想要放置它们，您可以使用display: grid;或display: flex;。
我试着当场写，因为这应该是一种可能性。

超文本标记语言

<div id="gallery">
    <div class="image-container">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>My Title<h2>
    </div>
    <div class="image-container">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>My Title<h2>
    </div>
    <div class="image-container">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>My Title<h2>
    </div>
    <div class="image-container">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>My Title<h2>
    </div>
    <div class="image-container">
        <img src="img/image-presentation.jpg" alt="image">
        <h2>My Title<h2>
    </div>
</div>

中央支助组

#projet .content .window #gallery {
    display: grid;
    column-gap: 50px;
    row-gap: 50px;
    grid-template-columns: auto auto auto;
    padding: 10px;
}

.image-container {
    position: relative;
    width: 300px;
    height: 500px;
}

.image-container img {
    width: 100%;
    height: 100%;
    transition: all 1s;
    z-index: 10;
}

.image-container img:hover {
    transform: translateY(-30px);
}

.image-container h2 {
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    opacity: 0;
}

.image-container img:hover+h2 {
    opacity: 1;
}