Multiple filters using FIrebase Functions (Server Side) - React JS

Question

I'm trying to create an application where you have multiple blogs about lost, found and up for adoption pets. You can filter this blogs by:

'Categories (Lost, found, up for adoption)', 'Animal type (Dog, cat, bird, rabbit, etc)', 'Hair type (no hair, short, medium, long)', 'Gender (Female, male)', 'Eyes type (...)', 'HasCollar(yes, no)'

I've done a working filter but it was on the client side and since I'm going to handle a large amount of data, that solution won't work. I've also tried to solve this problem using queries provided by firestore but I've come across with the limitation where I couldn't compare more than two categories. This was the code

    if (activeCategory !== 'All' && activeGender === 'All' && activeAnimal === 'All') {
    q = query(
        collection(db, "blogs"),
        where("category", "==", activeCategory),
        where("gender", "!=", activeGender),
        where("animal", "!=", activeAnimal),
        )

    onSnapshot(
        q,
        async (snapshot) => {
            
         let list = []

    snapshot.docs.forEach((doc) => {
        list.push({id: doc.id, ...doc.data()})
    })

 lastDoc = await snapshot.docs[snapshot.docs.length - 1]
 firstDoc = await snapshot.docs[0]


    list.sort((a, b) => (a.timestamp < b.timestamp) ? 1 : -1)

    setBlogs(list)
    setFilters(list)
    setLoading(false)
    setActive("home")
    setLastDoc(lastDoc)
    setFirstDoc(firstDoc)
        }, (error) => {
            console.log(error)
        }

    ) 
    
} else if{...} }

useEffect(() => {
  fetchData()
}, [activeCategory, activeGender, activeAnimal])

So my only option is to use Firebase functions. I've talked to a friend and he told me that I needed to have endpoints like this, for example

https/firebase.adoptar.com/api/filter? activeCategory=adopcion 

The thing is, I don't know how to do it or where to search information in order to learn about this. It has an structure resembling node js, right? So I'm trying to come up with a solution using firebase functions. Can someone help me or tell me where to search so I can learn how to do it? Or how a query should look like in order to multifilter and update the page's info according the filter?

I've read firebase functions documentation but at best it tells you how to do a CRUD operation, nothing about filtering or creating an endpoint like the one above.