tunning simple query with full-text

I would like tuning my query with full-text searching.

I have two tables:
1. artaolInventTable
a) IT_NAMEIDIDX (Unique, Non-clustered)
   - itemId
   - itemName
   (include column
b) IT_IMPORTIDX (Non-unique, non-clustered)
   - importIndex
c) IT_ITEMNAMEIDX (Unique, clustered)
   - itemName
d) PK_ARTAOLINVENTTABLE (Unique, non-clustered)
   - itemId

2. InventSumIntegration_ART
a) IS_AVAILIDX (Non-unique, Non-clustered)
   - availphysical
b) IS_ITEMIDX(Unique, Clustered)
   - itemId
   - availphysical

Query 1 - first I have simple query:

SELECT it.ItemId, it.ItemName, it.ItemBrand, it.Amount, it.salesunit, it.importIndex
FROM artaolInventTable IT
WHERE
(CONTAINS(it.ItemName, '("Papier*" OR FORMSOF(THESAURUS, Papier)) AND ("ksero*" OR FORMSOF(THESAURUS, ksero)) AND ("A4*" OR FORMSOF(THESAURUS, A4))')
OR it.importIndex = 'IP000' OR it.ItemId = 'aaaa' )
order by it.ItemName

CPU time = 32 ms,  elapsed time = 205 ms.

Execution plan looks good. To find every conditions in where clause sql use indexes.

Query 2 - I added second table and my execution time increased to 51 sec!. Why? Is there problem with my indexes? How I should build it?

INVENTSUMSHOPINTEGRATION has invent stock value.

SELECT IT.ITEMID, IT.ITEMNAME, IT.ITEMBRAND, IT.AMOUNT, IT.SALESUNIT, IT.ImportIndex, ISU.AVAILPHYSICAL 
FROM ARTAOLINVENTTABLE IT 
JOIN INVENTSUMSHOPINTEGRATION_ART ISU ON ISU.ITEMID = IT.ITEMID
WHERE 
(CONTAINS(IT.ITEMNAME, '("Papier*" OR FORMSOF(THESAURUS, Papier)) AND ("ksero*" OR FORMSOF(THESAURUS, ksero)) AND ("A4*" OR FORMSOF(THESAURUS, A4))')
OR IT.IMPORTINDEX = 'IP000' OR IT.ITEMID = 'aaaa' ) AND (ISU.AVAILPHYSICAL >= 0)
order by it.ITEMNAME

CPU time = 51418 ms,  elapsed time = 51756 ms.

save screenshots to disk to get good quality.

exection plan query 2

exection plan query 1

Best regards Jacek