21:25a

There are many more things that Jesus did: The phrase many more things refers to the many other miracles that Jesus did that John did not include in this Gospel. John did not write down everything he saw Jesus do. Here are other ways to translate this clause:

Jesus did many other things as well. (New International Version)
-or-
But Jesus did many things beside these.
-or-
There is much else that Jesus did. (Revised English Bible)

21:25b

If all of them were written down: This is an unfulfilled condition. Every one of Jesus’ miraculous acts was not written down. Only some of them were written down. Here are other ways to translate this clause:

If they were all written down one by one (Good News Translation)
-or-
If it all were to be recorded in detail (Revised English Bible)
-or-
If they were all written in books (Contemporary English Version)

all of them were written down: The verb phrase were written down is passive. There are at least two ways to translate it:

• Use a passive verb. For example:

it all were to be recorded (Revised English Bible)

• Use an active verb. For example:

If someone wrote down everything Jesus did

Use the verb form that is most natural in your language.

21:25c

I suppose that not even the world itself would have space for the books that would be written: This clause tells a result. The author imagines the result of having books that tell everything that Jesus did. He expresses the imagined result as an exaggeration, a figure of speech called a hyperbole. It does not mean that the world literally could not contain the books about everything that Jesus did. It just means that Jesus did many, many good miracles. There are two ways to translate this figure of speech:

• Keep the exaggeration. For example:

I think there would not be enough room in the world for all the books!
-or-
I think that the books written about him would fill all the libraries of the world!

• Remove the figure of speech. For example:

If everything that Jesus did was written down, it would take many many books to tell them all.

I suppose: The clause I suppose means “I think” or “I guess.” It introduces a statement that may or may not be true. The author thinks or supposes that it might be true.

not even the world itself would have space for the books that would be written: This clause means that there would be so many books about Jesus that people could not find room to put them all. Here are other ways to translate this clause:

even the whole world would not have room for the books that would be written (New International Version)
-or-
the world could not hold the books that would be written (Revised English Bible)
-or-
there would be no place/space for all the books that would be written

the books that would be written: The verb phrase would be written is passive. There are at least two ways to translate it:

• Use a passive verb. For example:

the books that would be written (NET Bible)

• Use an active verb. For example:

the books that people would write

Use the verb form that is most natural in your language in this context.

General Comment on 21:25c

In some languages it may be natural to translate this verse with the negative verb at the beginning. For example:

I do not suppose the world itself would hold all the books that would be written. (New Jerusalem Bible)
-or-
I do not suppose there would be room enough in the world for all the books people would have to write.