Connection to server lost - Too many traffic?


I host my own neo4j db (version 3.4.9 - Edition entreprise) .

And sometime I have this error (see on interface) :
BoltConnectionError: No connection found, did you connect to Neo4j? in neo4j interface and sometimes my application fail to connect to neo4j.

I think this problem become traffic on my site and many request (I think near 130/150K by days) in database and sometimes connection to neo4j is lost. But I don't know how to configure correctly neo4j (I have little knowledge in servers and configuration, I'm web developper)
So I hope somebody can help me to configure better my database (or maybe my server ?).

My database is in production and is very important to keep alive this database

This is server information (with top command)

Tasks: 260 total, 1 running, 259 sleeping, 0 stopped, 0 zombie
%Cpu(s): 30.4 us, 0.5 sy, 0.0 ni, 66.2 id, 0.0 wa, 0.0 hi, 2.9 si, 0.0 st
KiB Mem : 13198184+total, 4465908 free, 11890020+used, 8615728 buff/cache
KiB Swap: 1046520 total, 459516 free, 587004 used. 9714344 avail Mem

It's running on CentOS Linux release 7.5.1804 (Core)

If you need more information tell me