Is the series going to have more material for the anime than the manga?

Depends on the speed at which they will continue with the anime production and the way they'll plan the episodes. If they go at the pace they've been going at until now, then yes, the anime will most likely exceed the manga in the future - not on the second season, though, but maybe a third or fourth season might do that.
Also, I'm a bit confused by the wording you used, so I'll just clarify that the anime was never planned to follow any of the manga adaptations. The anime follows the LN directly. If you were already aware of this, sorry for misunderstanding your post!

The anime is going to exceed the manga. Most anime do. If you're looking for more of that universe, light novels are usually the best place to go for that.

@iuvin no it's me, I'm sorry for my bad english, so do you thing the anime will not care if it will exceed the manga? Knowing it will also impact the manga's selling?
I almost finished reading the manga part of the first season of the anime (40 chapters), but I forget a little bit if there is difference with the anime.

@Yaaceen manga are tie-in for the LN they are made to be both sold at the same time. Regardless of what the anime do. All popular LN get manga adaptation regardless of they get a anime adaptation which they eventually do.

@Yaaceen depend on the number of episodes, seasons and so on since no adaptation of LN really bother about the manga unless few exceptions. Which is why for LN adaptation what you want it's volumes adapted not what they did in the manga.

@Otakupervert890 I've read the first 40 manga chapters to remember what happened in the s1 of the anime, is there some major differences between the manga and the LN?

@Yaaceen no idea I rarely read manga of LN adaptation if the LN is available and in this case the LN go so far(12 volumes available in English with the 13th available for pre order) that I see no reason to read the manga.